Korean Journal of Cognitive and Biological Psychology, Dec 1, 2014
참조할 수 있는 외부 표지가 없는 상태에서, 잠깐 제시되는 시각표적의 위치를 정확히 보고하는 것은 쉽지 않다. 그런 상태에서는 시선의 방향과 같은 자기중심적 표지에 의존하게 ... more 참조할 수 있는 외부 표지가 없는 상태에서, 잠깐 제시되는 시각표적의 위치를 정확히 보고하는 것은 쉽지 않다. 그런 상태에서는 시선의 방향과 같은 자기중심적 표지에 의존하게 된다. 본 연구는 인간 참가자를 대상으로 자기중심적 위치 기억의 오류의 방향과 크기, 그리고 그 기전을 다루었다. 참가자가 암흑 상태에서 잠깐 보았던 시각표적의 위치에, 이후에 나타나는 탐사자극을 이동시키도록 하였다. 탐사자극을 사용하여 기억된 표적의 위치를 보고하는 행위 자체가 표적의 공간적 위치에 대한 기억을 왜곡함을 발견하였다. 탐사자극을 응시점과 같은 편에 처음 보여주면(SS 조건), 참가자는 탐사자극을 표적이 실제 있던 위치보다 응시점에서 체계적으로 더 멀리 이동시켰고, 탐사자극을 응시점을 기준으로 시각자극이 있던 위치의 반대편에 처음 보여주면(OS 조건), 비교적 정확하게 탐사자극을 표적의 실제 위치로 이동시켰다(실험 1). 탐사자극의 초기 위치에 따라 관찰되는 이러한 비대칭적인 왜곡은, 기억된 위치를 보고하는 동안 시선이 어디를 향하는가에 따라 달라지지 않았으며(실험 2), 위치를 보고하는데 사용한 장치에 따라서도 달라지지 않았다(실험 3). 관찰된 왜곡 패턴은, 지각된 표적의 위치가 탐사자극과 응시점 모두로부터 반발된다는 가정 하에서 예측되는 결과와 일치하였다. 공간적 배열에 따라서, 응시점과 탐사자극으로부터의 반발이 동일한 방향으로 누적되어 표적의 이심도를 실제보다 더 크게 보고하기도 하고(SS 조건), 반대 방향으로 작용하여 서로 상쇄되어 상대적으로 정확한 보고를 하기도 하였다(OS 조건).
A focal stimulus outside the receptive field robustly induces LFP change, while the same stimulus... more A focal stimulus outside the receptive field robustly induces LFP change, while the same stimulus evokes no spike activity. We determined how this subthreshold LFP change interacted with spike response to the RF stimulus. Specifically, we sequentially presented two identical Gabor stimuli with a variable stimulus onset asynchrony (SOA); the first one (S1) was presented outside RF inducing a subthreshold LFP change, and the second one (S2) was subsequently presented within RF generating a spiking response. This enabled us to manipulate the temporal relation between subthreshold LFP and evoked spike activity and to determine whether subthreshold LFP contributed to modulation of spike activity in a SOA-dependent manner. We found that the subthreshold LFP propagated a considerably long distance, estimated to be more than 10 mm of cortical distance. The cross-correlation between the time course of subthreshold LFP and the pattern of SOA-dependency of spike activity was significant. These results indicate that signal integration is farther beyond the RF than previously estimated based on spike-triggered average, and suggest that subthreshold LFP modulate spike activity in a SOA-dependent manner.
<p>Each dot represents selectivity index (SI) for each stimulus condition and anatomical di... more <p>Each dot represents selectivity index (SI) for each stimulus condition and anatomical distance between the centers of S1 and S2 for that condition. Mariginal histograms are also shown. The cortical distance was estimated from the cortical magnification factor <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047543#pone.0047543-Horton1" target="_blank">[31]</a>. Data are combined single and multiple unit data obtained from 227 stimulus conditions (i.e., S1 positions) for 105 recording sites in 2 monkeys. Black dots and bars indicate significant <i>SIs</i> (69 of 227 cases, 30.40%, p<0.05), as evaluated with a bootstrapping method. The proportion was also consistent for single units alone (23 of 92 stimulus conditions, 25%) and multiple unit activitiy (46 of 135 stimulus conditions, 34.07%).The proportion of significant <i>SI</i> decreased with the cortical distance between S1 and S2.</p
<p><b>A.</b> Shown are LFP traces in an arbitrary unit for each SOA condition d... more <p><b>A.</b> Shown are LFP traces in an arbitrary unit for each SOA condition derived by the mean LFP traces observed during S1-S2 sequence stimulation minus the SOA-adjusted linear sum of S1-evoked LFP and S2-evoked LFP. <b>B.</b> Deviation of LFP in RMS power. Each colored symbol represents the mean deviation across SOA conditions for each of 30 cells shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0144929#pone.0144929.g005" target="_blank">Fig 5</a>. Black symbols represent their mean values with 1SEs.</p
<p><b>A.</b> SOA-dependent spike modulation for the cell shown in <a href=&q... more <p><b>A.</b> SOA-dependent spike modulation for the cell shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0144929#pone.0144929.g003" target="_blank">Fig 3</a>. The mean firing rates during the post-stimulus period of 50–150 ms of S2 are plotted as a function of SOA. Vertical dashed lines are the reference response levels evoked by S2 alone. <b>B.</b> Simultaneously recorded mean LFP traces in an arbitrary unit for corresponding SOAs for the cell shown in A. Traces are vertically shifted for visibility. <b>C.</b> Time course of mean correlation between spike and LFP modulation. The correlation coefficient between the SOA-dependent firing rate (as shown in A) and the instantaneous amplitude of LFP (as shown in B) was first calculated every 1 ms for each condition. Shown is the mean correlation coefficient time course averaged over all 517 stimulus conditions (11 SOAs X 47 S1-S2 sequences) from 31 cells including cases in which S1 was tested at more than one RF diameter away. The shading represents ±1 SE. Note a positive correlation immediately after S2 onset (arrow) and a subsequent negative correlation. <b>D, E.</b> Frequency histograms of the time from S2 onset (D) and the correlation coefficient (E) for the 1<sup>st</sup> (upper) and 2<sup>nd</sup> (lower) peaks in the time course of correlation. Dashed vertical lines indicate distribution means. For the 1<sup>st</sup> peak correlation, the mean location was 45.25 ±36.0 ms and the mean correlation coefficient was 0.32 ±0.24. For the 2<sup>nd</sup> peak, the mean location was 119.32 ±38.3 ms, and the mean correlation coefficient was -0.42 ±0.33. Black bars indicate significant cases, as determined with a bootstrap statistical test (p<0.05).</p
<p>(A) Spatial relation between stimuli in screen coordinates (calibration bar = 1 deg). Wh... more <p>(A) Spatial relation between stimuli in screen coordinates (calibration bar = 1 deg). White cross represents fixation target, and the dashed circle (invisible to the animal) encloses the RF of the recorded neuron determined with a spatial summation test. Gabor stimulus at RF (S2) is at preferrred orientation. S1 was presented at one of four locations, a–d, along the axis orthogonal to that of RF orientation, with a spacing of one RF diameter. All S1 orientations were parallel to S2. There were 44 unique stimulus sequences (4 S1 positions×11 SOAs), plus five single stimulus conditions at each S1 and S2 locations. These 49 stimulus conditions were randomly repeated. (B) Raster and density plots of response to S1 at positions a–d aligned at its onset. Spike density function was derived by convolving spike sequence with an asymmetric kernel function <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047543#pone.0047543-Thompson1" target="_blank">[66]</a>. Y-axis indicates spike density in spikes/s. Note that no S1 alone at positions a-d evoked spike response. (C) Raster and density plots for S2 alone and S1c-S2 sequence stimuli with SOAs of 30 and 50 ms chosen to illustrate response modulation. Trials are aligned at S2 onset. It can be seen that the magnitude of initial and sustained response varied with SOA. (D) An example SOA-time plot compiled from spike density for S1c-S2 sequence stimuli, the first stimulus at positions c and the second stimulus at RF. Y-axis is SOA, determined in 10-ms step. The times of S1 onset for each SOA condition are indicated as small white circles. Data are linearly interpolated across SOA. The S2-alone condition is given above for comparison. Note that the cell’s response varied with SOA. (E) Determination of significant modulation. Spike density curves for S2 alone (black) and S1c-S2 sequence with SOA of 80 ms (green), along with horizotal marks (top) of temporal epochs associated with statistically significant decrease (blue) and increase (red) from S2 alone condition. (F) Time course of significant modulation of spike response by sequence stimuli as shown in E. Spike density following S1–S2 sequence was compared with spike density following S2 for each of temporal epochs of 30 ms with a shift of 5 ms. The temporal epochs with a statistically-significant decrease in spike density as determined with Mann-Whitney U-test are shown in blue bars, and significant increase in red bars, centering on corresponding analysis windows, revealing the magnitude and time course of suppressive and facilitative effects of S1 that depend on S1 position and SOA. The dark symbols represent significant modulation at p<0.01, and the light ones are p<0.05.</p
A focal stimulus outside the receptive field robustly induces LFP change, while the same stimulus... more A focal stimulus outside the receptive field robustly induces LFP change, while the same stimulus evokes no spike activity. We determined how this subthreshold LFP change interacted with spike response to the RF stimulus. Specifically, we sequentially presented two identical Gabor stimuli with a variable stimulus onset asynchrony (SOA); the first one (S1) was presented outside RF inducing a subthreshold LFP change, and the second one (S2) was subsequently presented within RF generating a spiking response. This enabled us to manipulate the temporal relation between subthreshold LFP and evoked spike activity and to determine whether subthreshold LFP contributed to modulation of spike activity in a SOA-dependent manner. We found that the subthreshold LFP propagated a considerably long distance, estimated to be more than 10 mm of cortical distance. The cross-correlation between the time course of subthreshold LFP and the pattern of SOA-dependency of spike activity was significant. These results indicate that signal integration is farther beyond the RF than previously estimated based on spike-triggered average, and suggest that subthreshold LFP modulate spike activity in a SOA-dependent manner.
Visually guided saccadic eye movements are thought to involve multiple stages of processing in di... more Visually guided saccadic eye movements are thought to involve multiple stages of processing in diverse brain structures including the primary visual cortex (V1). The variability of neural activity in each of these structures may present ambiguities for downstream stages in identifying sensory and motor signals among spontaneous discharges. The response time of saccadic eye movements made toward a visual target is correlated with the time of the first spikes in V1 that are evoked by the target (Lee et al., 2010). This suggests that downstream neurons receiving the output of V1 are faced with a challenging task of discriminating first spikes of visual response against spontaneous discharge. Here we report a novel response property of the macaque V1 neurons. Immediately before neurons discharge a burst of activity to a visual saccade target, spontaneous discharges were transiently suppressed. This suppression was maximal ϳ18 ms after target onset. Based on simulations of artificial spike trains, we propose that the transient suppression enhances temporal contrast for identifying the onset of visual response by increasing the reliability of detection of response onset by downstream neurons, thereby facilitating visually guided behavioral responses.
<p>Each colored symbol represents the mean magnitude of spike (A) or LFP (B) response in pe... more <p>Each colored symbol represents the mean magnitude of spike (A) or LFP (B) response in percentage with respect to S2-alone condition for corresponding SOA condition of each of 30 cells for which nearest S1 was tested. Black symbols represent median values of those means with 1SEs. Percent modulations less than 100 indicate suppression and those larger than 100 indicate facilitation by addition of S1.</p
32 33 Single neurons in the primary visual cortex (V1) show variability in spike activity in resp... more 32 33 Single neurons in the primary visual cortex (V1) show variability in spike activity in response to 34 an identical visual stimulus. In the current study, we examined the behavioral consequences of 35 the variability in spike activity of V1 neurons for visually-guided saccades. We recorded single 36 cell activity from V1 of monkeys trained to detect and make saccades toward visual targets of 37 varying contrast, and analyzed trial-to-trial covariation between the onset time or firing rate of 38 neural response and saccadic response time (RT). Neural latency (NL, the time of the first 39 spike of neural response) was correlated with RT, whereas firing rate (FR) was not. When FR 40 was computed with respect to target onset ignoring NL, a ‘false’ correlation between FR and RT 41 emerged. Multiple regression and partial correlation analyses on NL and FR for predictability of 42 RT variability, as well as a simulation with artificial Poisson spike trains, supported the 43 conclusion...
112 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1986.The primary visual pathway... more 112 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1986.The primary visual pathway consists of projections from the retina to the lateral geniculate nucleus (LGN) and from the LGN to the visual cortex. The cat LGN has 3 major subdivisions containing independent representations of visual space: A layers, C layers, and the medial interlaminar nucleus (MIN). The visual cortex has more than 10 areas thought to process different aspects of vision. This thesis is about the functional organization of one of these cortical areas, the Clare-Bishop area, its geniculate afferent pathways, and its participation in associational cortical circuits. My basic findings are: (i) The MIN represents an area of the retina coincident with the reflective tapetum (Lee et al., 1984). Cells of the MIN have greater sensitivity in the dark than do the cells of other geniculate subdivisions. These findings suggest that the MIN is related to dim light vision. (ii) Associational input from area 18 is organized into a stripe-like pattern of inputs to the Clare-Bishop area that is under control of layer A. The influence of the MIN appears to be maximal in an interdigitating series of stripes, and there is some evidence of inhibitory interaction between the MIN- and layer A-dependent regions of the Clare-Bishop area. (iii) High acuity information is relayed through layer A to the Clare-Bishop area via simple cells of area 18. Some of these simple cells have receptive field properties suitable for 3-dimensional motion detection. (iv) Simple cells are largely under control of layer A, as in area 17 (Malpeli, 1983). Complex cells in both areas are in general independent of layer A.Based on these results, I propose a theory of the Clare-Bishop area that involves parcellation and functional switching of cortical tissue for most efficient processing under both bright-light (high acuity) and dim-light (high sensitivity) conditions.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD
1. The cat medial interlaminar nucleus (MIN) receives inputs almost exclusively from tapetal reti... more 1. The cat medial interlaminar nucleus (MIN) receives inputs almost exclusively from tapetal retina, suggesting that the MIN has a special role in dim-light vision. In this study we compared the sensitivities of cells in the MIN with those in layers A and magnocellular C of the lateral geniculate nucleus (LGNd), using drifting sinusoidal gratings to determine contrast thresholds as a function of spatial frequency and retinal adaptation level over the entire scotopic range. 2. About one-half of the cells recorded in the MIN and layer A had brisk responses that could be nulled by properly positioned, counterphased sinusoidal gratings, and were classified as X cells. The rest of the cells in the MIN and layer A, as well as all cells recorded in layer C, were Y cells. 3. MIN cells had higher contrast sensitivity than layer A cells for low spatial frequencies (0.15 cycles/deg and below) over a wide range of adaptation levels, both overall and for separate comparisons within X or Y cells....
A focal visual stimulus outside the classical receptive field (RF) of a V1 neuron does not evoke ... more A focal visual stimulus outside the classical receptive field (RF) of a V1 neuron does not evoke a spike response by itself, and yet evokes robust changes in the local field potential (LFP). This subthreshold LFP provides a unique opportunity to investigate how changes induced by surround stimulation leads to modulation of spike activity. In the current study, two identical Gabor stimuli were sequentially presented with a variable stimulus onset asynchrony (SOA) ranging from 0 to 100 ms: the first (S1) outside the RF and the second (S2) over the RF of primary visual cortex neurons, while trained monkeys performed a fixation task. This focal and asynchronous stimulation of the RF surround enabled us to analyze the modulation of S2-evoked spike activity and covariation between spike and LFP modulation across SOA. In this condition, the modulation of S2-evoked spike response was dominantly facilitative and was correlated with the change in LFP amplitude, which was pronounced for the cells recorded in the upper cortical layers. The time course of covariation between the SOA-dependent spike modulation and LFP amplitude suggested that the subthreshold LFP evoked by the S1 can predict the magnitude of upcoming spike modulation.
Spike activity of V1 neurons in response to natural scene (Vinje and Gallant, 2002; Montemurro et... more Spike activity of V1 neurons in response to natural scene (Vinje and Gallant, 2002; Montemurro et al., 2008; Haider et al., 2010) is surprisingly consistent across repeated trials. While it is clear that these responses are not explained by classical receptive field (cRF) properties, it is not known how surround interaction increases the selectivity of V1 response. Put more generally, we do not completely understand the mapping rules between elementary features of visual scene and V1 activity. In the current study we examined the possibility that V1 neurons are selective for spatiotemporal sequence of oriented stimuli. We will describe a novel response property of monkey V1 neurons that visual response was modulated depending on the stimulus onset asynchrony (SOA) in the range of tens of milliseconds between two sequentially presented Gabor stimuli. The preceding stimulus (S1) was presented outside cRF and the following one (S2) inside cRF. S1 alone did not evoke spike response but modulated cell's response to S2. Spike response to S2 was not constant across SOA, and the SOA associated with maximal response modulation varied with the position of S1. These results suggest that V1 neurons are selective for spatiotemporal sequence of oriented stimuli based on surround interaction.
Simultaneous recording of eye and head movements during reading revealed that head movements cons... more Simultaneous recording of eye and head movements during reading revealed that head movements consisted of two components: a modulatory-velocity component coupled to eye saccades, and a constant-velocity component that was independent of eye saccades. Whereas the constant-velocity component increased as subjects repeatedly read the same text, neither the magnitude of the modulatory-velocity component, nor the amplitude of the eye movement, increased. This outcome could be closely simulated when the head movement command was assumed to be stronger, and issued earlier with repeated reading. These results suggest that higher-level processes related to text familiarity modulate eye-head coordination through head movements.
The morphological and laminar characteristics of the dorsal lateral geniculate nucleus (LGN) and ... more The morphological and laminar characteristics of the dorsal lateral geniculate nucleus (LGN) and medial interlaminar nucleus (MIN) of the domestic dog (Canis familiaris) were studied by three-dimensional computer reconstruction of labeled retinal afferents following intraocular HRP injections. As previously reported, the dog LGN consisted of layers A, A1, C, C1, C2, and C3. Layers A, C, and C2 receive contralateral-eye inputs, and layers A1 and C1 ipsilateral inputs. The dog MIN was found to have four orderly interdigitating layers; layers 1, 2, 3, and 4, medial to lateral. MIN layers 1 and 3 received contralateral inputs, and layers 2 and 4 ipsilateral inputs. Layer 1 had the largest soma of all LGN/MIN layers. LGN layer A was partially separated into medial and lateral subdivisions by a cleft free of somata. The overall three-dimensional shape of the lateral geniculate body was like the letter C, with the convex part of the C directed posteriorly. The relative volume of the MIN was smaller than in the cat; the canine MIN comprised 8.3% of the combined volume of layers A, A1 and the MIN, while that of the cat comprised 14.2% as estimated from Sanderson&#39;s map. The volume of all contralateral-eye layers, combining both LGN and MIN, was 31.2 mm(3) (78%), and that for ipsilateral layers was 8.6 mm(3) (22%). The ratio of ipsilateral to contralateral laminar volumes is much lower in the dog than in the cat.
In this study, we examined functional contributions of major subdivisions of the lateral genicula... more In this study, we examined functional contributions of major subdivisions of the lateral geniculate nucleus to the cat's lateral suprasylvian visual area (LS) in relation to the patchy horizontal distributions of association inputs. Multiple-unit activity driven via the contralateral eye was assessed during reversible blockade of the retinotopically corresponding part of layer A, the C layers as a group, or the medial interlaminar nucleus (MIN). Inactivating each of these targets reduced activity at some cortical sites, with inactivation of layer A having, on average, the largest effect. Activity was rarely abolished by inactivation of a single target, indicating that most LS sites receive multiple inputs. Dependence on layer A was strongly correlated with the horizontal distribution of association inputs from area 18. Closely spaced injections of anatomical tracers into extensive regions of area 18 resulted in patches of terminal label in lateral suprasylvian cortex. Activity i...
The goal of this study was to determine the effects of inactivating layer A or the C layers of th... more The goal of this study was to determine the effects of inactivating layer A or the C layers of the cat lateral geniculate nucleus on the supragranular layers of area 18, including cells antidromically activated from the lateral suprasylvian visual area (LS). Isolated cells were visually driven via the contralateral eye while the retinotopically corresponding regions of layer A or, in some cases, the C layers were reversibly inactivated with injections of cobaltous chloride. Simple cells were frequently encountered and were on average more dependent upon layer A than were complex cells, a result qualitatively similar to that found previously in area 17 (Malpeli, 1983; Malpeli et al., 1986). However, the influence of the C layers on area 18 was much more apparent than for area 17. In area 18, as in area 17, the dependence of simple cells on particular geniculate layers appears to follow the terminal patterns of the major direct geniculate inputs. Those simple cells most dependent on l...
Korean Journal of Cognitive and Biological Psychology, Dec 1, 2014
참조할 수 있는 외부 표지가 없는 상태에서, 잠깐 제시되는 시각표적의 위치를 정확히 보고하는 것은 쉽지 않다. 그런 상태에서는 시선의 방향과 같은 자기중심적 표지에 의존하게 ... more 참조할 수 있는 외부 표지가 없는 상태에서, 잠깐 제시되는 시각표적의 위치를 정확히 보고하는 것은 쉽지 않다. 그런 상태에서는 시선의 방향과 같은 자기중심적 표지에 의존하게 된다. 본 연구는 인간 참가자를 대상으로 자기중심적 위치 기억의 오류의 방향과 크기, 그리고 그 기전을 다루었다. 참가자가 암흑 상태에서 잠깐 보았던 시각표적의 위치에, 이후에 나타나는 탐사자극을 이동시키도록 하였다. 탐사자극을 사용하여 기억된 표적의 위치를 보고하는 행위 자체가 표적의 공간적 위치에 대한 기억을 왜곡함을 발견하였다. 탐사자극을 응시점과 같은 편에 처음 보여주면(SS 조건), 참가자는 탐사자극을 표적이 실제 있던 위치보다 응시점에서 체계적으로 더 멀리 이동시켰고, 탐사자극을 응시점을 기준으로 시각자극이 있던 위치의 반대편에 처음 보여주면(OS 조건), 비교적 정확하게 탐사자극을 표적의 실제 위치로 이동시켰다(실험 1). 탐사자극의 초기 위치에 따라 관찰되는 이러한 비대칭적인 왜곡은, 기억된 위치를 보고하는 동안 시선이 어디를 향하는가에 따라 달라지지 않았으며(실험 2), 위치를 보고하는데 사용한 장치에 따라서도 달라지지 않았다(실험 3). 관찰된 왜곡 패턴은, 지각된 표적의 위치가 탐사자극과 응시점 모두로부터 반발된다는 가정 하에서 예측되는 결과와 일치하였다. 공간적 배열에 따라서, 응시점과 탐사자극으로부터의 반발이 동일한 방향으로 누적되어 표적의 이심도를 실제보다 더 크게 보고하기도 하고(SS 조건), 반대 방향으로 작용하여 서로 상쇄되어 상대적으로 정확한 보고를 하기도 하였다(OS 조건).
A focal stimulus outside the receptive field robustly induces LFP change, while the same stimulus... more A focal stimulus outside the receptive field robustly induces LFP change, while the same stimulus evokes no spike activity. We determined how this subthreshold LFP change interacted with spike response to the RF stimulus. Specifically, we sequentially presented two identical Gabor stimuli with a variable stimulus onset asynchrony (SOA); the first one (S1) was presented outside RF inducing a subthreshold LFP change, and the second one (S2) was subsequently presented within RF generating a spiking response. This enabled us to manipulate the temporal relation between subthreshold LFP and evoked spike activity and to determine whether subthreshold LFP contributed to modulation of spike activity in a SOA-dependent manner. We found that the subthreshold LFP propagated a considerably long distance, estimated to be more than 10 mm of cortical distance. The cross-correlation between the time course of subthreshold LFP and the pattern of SOA-dependency of spike activity was significant. These results indicate that signal integration is farther beyond the RF than previously estimated based on spike-triggered average, and suggest that subthreshold LFP modulate spike activity in a SOA-dependent manner.
<p>Each dot represents selectivity index (SI) for each stimulus condition and anatomical di... more <p>Each dot represents selectivity index (SI) for each stimulus condition and anatomical distance between the centers of S1 and S2 for that condition. Mariginal histograms are also shown. The cortical distance was estimated from the cortical magnification factor <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047543#pone.0047543-Horton1" target="_blank">[31]</a>. Data are combined single and multiple unit data obtained from 227 stimulus conditions (i.e., S1 positions) for 105 recording sites in 2 monkeys. Black dots and bars indicate significant <i>SIs</i> (69 of 227 cases, 30.40%, p<0.05), as evaluated with a bootstrapping method. The proportion was also consistent for single units alone (23 of 92 stimulus conditions, 25%) and multiple unit activitiy (46 of 135 stimulus conditions, 34.07%).The proportion of significant <i>SI</i> decreased with the cortical distance between S1 and S2.</p
<p><b>A.</b> Shown are LFP traces in an arbitrary unit for each SOA condition d... more <p><b>A.</b> Shown are LFP traces in an arbitrary unit for each SOA condition derived by the mean LFP traces observed during S1-S2 sequence stimulation minus the SOA-adjusted linear sum of S1-evoked LFP and S2-evoked LFP. <b>B.</b> Deviation of LFP in RMS power. Each colored symbol represents the mean deviation across SOA conditions for each of 30 cells shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0144929#pone.0144929.g005" target="_blank">Fig 5</a>. Black symbols represent their mean values with 1SEs.</p
<p><b>A.</b> SOA-dependent spike modulation for the cell shown in <a href=&q... more <p><b>A.</b> SOA-dependent spike modulation for the cell shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0144929#pone.0144929.g003" target="_blank">Fig 3</a>. The mean firing rates during the post-stimulus period of 50–150 ms of S2 are plotted as a function of SOA. Vertical dashed lines are the reference response levels evoked by S2 alone. <b>B.</b> Simultaneously recorded mean LFP traces in an arbitrary unit for corresponding SOAs for the cell shown in A. Traces are vertically shifted for visibility. <b>C.</b> Time course of mean correlation between spike and LFP modulation. The correlation coefficient between the SOA-dependent firing rate (as shown in A) and the instantaneous amplitude of LFP (as shown in B) was first calculated every 1 ms for each condition. Shown is the mean correlation coefficient time course averaged over all 517 stimulus conditions (11 SOAs X 47 S1-S2 sequences) from 31 cells including cases in which S1 was tested at more than one RF diameter away. The shading represents ±1 SE. Note a positive correlation immediately after S2 onset (arrow) and a subsequent negative correlation. <b>D, E.</b> Frequency histograms of the time from S2 onset (D) and the correlation coefficient (E) for the 1<sup>st</sup> (upper) and 2<sup>nd</sup> (lower) peaks in the time course of correlation. Dashed vertical lines indicate distribution means. For the 1<sup>st</sup> peak correlation, the mean location was 45.25 ±36.0 ms and the mean correlation coefficient was 0.32 ±0.24. For the 2<sup>nd</sup> peak, the mean location was 119.32 ±38.3 ms, and the mean correlation coefficient was -0.42 ±0.33. Black bars indicate significant cases, as determined with a bootstrap statistical test (p<0.05).</p
<p>(A) Spatial relation between stimuli in screen coordinates (calibration bar = 1 deg). Wh... more <p>(A) Spatial relation between stimuli in screen coordinates (calibration bar = 1 deg). White cross represents fixation target, and the dashed circle (invisible to the animal) encloses the RF of the recorded neuron determined with a spatial summation test. Gabor stimulus at RF (S2) is at preferrred orientation. S1 was presented at one of four locations, a–d, along the axis orthogonal to that of RF orientation, with a spacing of one RF diameter. All S1 orientations were parallel to S2. There were 44 unique stimulus sequences (4 S1 positions×11 SOAs), plus five single stimulus conditions at each S1 and S2 locations. These 49 stimulus conditions were randomly repeated. (B) Raster and density plots of response to S1 at positions a–d aligned at its onset. Spike density function was derived by convolving spike sequence with an asymmetric kernel function <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047543#pone.0047543-Thompson1" target="_blank">[66]</a>. Y-axis indicates spike density in spikes/s. Note that no S1 alone at positions a-d evoked spike response. (C) Raster and density plots for S2 alone and S1c-S2 sequence stimuli with SOAs of 30 and 50 ms chosen to illustrate response modulation. Trials are aligned at S2 onset. It can be seen that the magnitude of initial and sustained response varied with SOA. (D) An example SOA-time plot compiled from spike density for S1c-S2 sequence stimuli, the first stimulus at positions c and the second stimulus at RF. Y-axis is SOA, determined in 10-ms step. The times of S1 onset for each SOA condition are indicated as small white circles. Data are linearly interpolated across SOA. The S2-alone condition is given above for comparison. Note that the cell’s response varied with SOA. (E) Determination of significant modulation. Spike density curves for S2 alone (black) and S1c-S2 sequence with SOA of 80 ms (green), along with horizotal marks (top) of temporal epochs associated with statistically significant decrease (blue) and increase (red) from S2 alone condition. (F) Time course of significant modulation of spike response by sequence stimuli as shown in E. Spike density following S1–S2 sequence was compared with spike density following S2 for each of temporal epochs of 30 ms with a shift of 5 ms. The temporal epochs with a statistically-significant decrease in spike density as determined with Mann-Whitney U-test are shown in blue bars, and significant increase in red bars, centering on corresponding analysis windows, revealing the magnitude and time course of suppressive and facilitative effects of S1 that depend on S1 position and SOA. The dark symbols represent significant modulation at p<0.01, and the light ones are p<0.05.</p
A focal stimulus outside the receptive field robustly induces LFP change, while the same stimulus... more A focal stimulus outside the receptive field robustly induces LFP change, while the same stimulus evokes no spike activity. We determined how this subthreshold LFP change interacted with spike response to the RF stimulus. Specifically, we sequentially presented two identical Gabor stimuli with a variable stimulus onset asynchrony (SOA); the first one (S1) was presented outside RF inducing a subthreshold LFP change, and the second one (S2) was subsequently presented within RF generating a spiking response. This enabled us to manipulate the temporal relation between subthreshold LFP and evoked spike activity and to determine whether subthreshold LFP contributed to modulation of spike activity in a SOA-dependent manner. We found that the subthreshold LFP propagated a considerably long distance, estimated to be more than 10 mm of cortical distance. The cross-correlation between the time course of subthreshold LFP and the pattern of SOA-dependency of spike activity was significant. These results indicate that signal integration is farther beyond the RF than previously estimated based on spike-triggered average, and suggest that subthreshold LFP modulate spike activity in a SOA-dependent manner.
Visually guided saccadic eye movements are thought to involve multiple stages of processing in di... more Visually guided saccadic eye movements are thought to involve multiple stages of processing in diverse brain structures including the primary visual cortex (V1). The variability of neural activity in each of these structures may present ambiguities for downstream stages in identifying sensory and motor signals among spontaneous discharges. The response time of saccadic eye movements made toward a visual target is correlated with the time of the first spikes in V1 that are evoked by the target (Lee et al., 2010). This suggests that downstream neurons receiving the output of V1 are faced with a challenging task of discriminating first spikes of visual response against spontaneous discharge. Here we report a novel response property of the macaque V1 neurons. Immediately before neurons discharge a burst of activity to a visual saccade target, spontaneous discharges were transiently suppressed. This suppression was maximal ϳ18 ms after target onset. Based on simulations of artificial spike trains, we propose that the transient suppression enhances temporal contrast for identifying the onset of visual response by increasing the reliability of detection of response onset by downstream neurons, thereby facilitating visually guided behavioral responses.
<p>Each colored symbol represents the mean magnitude of spike (A) or LFP (B) response in pe... more <p>Each colored symbol represents the mean magnitude of spike (A) or LFP (B) response in percentage with respect to S2-alone condition for corresponding SOA condition of each of 30 cells for which nearest S1 was tested. Black symbols represent median values of those means with 1SEs. Percent modulations less than 100 indicate suppression and those larger than 100 indicate facilitation by addition of S1.</p
32 33 Single neurons in the primary visual cortex (V1) show variability in spike activity in resp... more 32 33 Single neurons in the primary visual cortex (V1) show variability in spike activity in response to 34 an identical visual stimulus. In the current study, we examined the behavioral consequences of 35 the variability in spike activity of V1 neurons for visually-guided saccades. We recorded single 36 cell activity from V1 of monkeys trained to detect and make saccades toward visual targets of 37 varying contrast, and analyzed trial-to-trial covariation between the onset time or firing rate of 38 neural response and saccadic response time (RT). Neural latency (NL, the time of the first 39 spike of neural response) was correlated with RT, whereas firing rate (FR) was not. When FR 40 was computed with respect to target onset ignoring NL, a ‘false’ correlation between FR and RT 41 emerged. Multiple regression and partial correlation analyses on NL and FR for predictability of 42 RT variability, as well as a simulation with artificial Poisson spike trains, supported the 43 conclusion...
112 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1986.The primary visual pathway... more 112 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1986.The primary visual pathway consists of projections from the retina to the lateral geniculate nucleus (LGN) and from the LGN to the visual cortex. The cat LGN has 3 major subdivisions containing independent representations of visual space: A layers, C layers, and the medial interlaminar nucleus (MIN). The visual cortex has more than 10 areas thought to process different aspects of vision. This thesis is about the functional organization of one of these cortical areas, the Clare-Bishop area, its geniculate afferent pathways, and its participation in associational cortical circuits. My basic findings are: (i) The MIN represents an area of the retina coincident with the reflective tapetum (Lee et al., 1984). Cells of the MIN have greater sensitivity in the dark than do the cells of other geniculate subdivisions. These findings suggest that the MIN is related to dim light vision. (ii) Associational input from area 18 is organized into a stripe-like pattern of inputs to the Clare-Bishop area that is under control of layer A. The influence of the MIN appears to be maximal in an interdigitating series of stripes, and there is some evidence of inhibitory interaction between the MIN- and layer A-dependent regions of the Clare-Bishop area. (iii) High acuity information is relayed through layer A to the Clare-Bishop area via simple cells of area 18. Some of these simple cells have receptive field properties suitable for 3-dimensional motion detection. (iv) Simple cells are largely under control of layer A, as in area 17 (Malpeli, 1983). Complex cells in both areas are in general independent of layer A.Based on these results, I propose a theory of the Clare-Bishop area that involves parcellation and functional switching of cortical tissue for most efficient processing under both bright-light (high acuity) and dim-light (high sensitivity) conditions.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD
1. The cat medial interlaminar nucleus (MIN) receives inputs almost exclusively from tapetal reti... more 1. The cat medial interlaminar nucleus (MIN) receives inputs almost exclusively from tapetal retina, suggesting that the MIN has a special role in dim-light vision. In this study we compared the sensitivities of cells in the MIN with those in layers A and magnocellular C of the lateral geniculate nucleus (LGNd), using drifting sinusoidal gratings to determine contrast thresholds as a function of spatial frequency and retinal adaptation level over the entire scotopic range. 2. About one-half of the cells recorded in the MIN and layer A had brisk responses that could be nulled by properly positioned, counterphased sinusoidal gratings, and were classified as X cells. The rest of the cells in the MIN and layer A, as well as all cells recorded in layer C, were Y cells. 3. MIN cells had higher contrast sensitivity than layer A cells for low spatial frequencies (0.15 cycles/deg and below) over a wide range of adaptation levels, both overall and for separate comparisons within X or Y cells....
A focal visual stimulus outside the classical receptive field (RF) of a V1 neuron does not evoke ... more A focal visual stimulus outside the classical receptive field (RF) of a V1 neuron does not evoke a spike response by itself, and yet evokes robust changes in the local field potential (LFP). This subthreshold LFP provides a unique opportunity to investigate how changes induced by surround stimulation leads to modulation of spike activity. In the current study, two identical Gabor stimuli were sequentially presented with a variable stimulus onset asynchrony (SOA) ranging from 0 to 100 ms: the first (S1) outside the RF and the second (S2) over the RF of primary visual cortex neurons, while trained monkeys performed a fixation task. This focal and asynchronous stimulation of the RF surround enabled us to analyze the modulation of S2-evoked spike activity and covariation between spike and LFP modulation across SOA. In this condition, the modulation of S2-evoked spike response was dominantly facilitative and was correlated with the change in LFP amplitude, which was pronounced for the cells recorded in the upper cortical layers. The time course of covariation between the SOA-dependent spike modulation and LFP amplitude suggested that the subthreshold LFP evoked by the S1 can predict the magnitude of upcoming spike modulation.
Spike activity of V1 neurons in response to natural scene (Vinje and Gallant, 2002; Montemurro et... more Spike activity of V1 neurons in response to natural scene (Vinje and Gallant, 2002; Montemurro et al., 2008; Haider et al., 2010) is surprisingly consistent across repeated trials. While it is clear that these responses are not explained by classical receptive field (cRF) properties, it is not known how surround interaction increases the selectivity of V1 response. Put more generally, we do not completely understand the mapping rules between elementary features of visual scene and V1 activity. In the current study we examined the possibility that V1 neurons are selective for spatiotemporal sequence of oriented stimuli. We will describe a novel response property of monkey V1 neurons that visual response was modulated depending on the stimulus onset asynchrony (SOA) in the range of tens of milliseconds between two sequentially presented Gabor stimuli. The preceding stimulus (S1) was presented outside cRF and the following one (S2) inside cRF. S1 alone did not evoke spike response but modulated cell's response to S2. Spike response to S2 was not constant across SOA, and the SOA associated with maximal response modulation varied with the position of S1. These results suggest that V1 neurons are selective for spatiotemporal sequence of oriented stimuli based on surround interaction.
Simultaneous recording of eye and head movements during reading revealed that head movements cons... more Simultaneous recording of eye and head movements during reading revealed that head movements consisted of two components: a modulatory-velocity component coupled to eye saccades, and a constant-velocity component that was independent of eye saccades. Whereas the constant-velocity component increased as subjects repeatedly read the same text, neither the magnitude of the modulatory-velocity component, nor the amplitude of the eye movement, increased. This outcome could be closely simulated when the head movement command was assumed to be stronger, and issued earlier with repeated reading. These results suggest that higher-level processes related to text familiarity modulate eye-head coordination through head movements.
The morphological and laminar characteristics of the dorsal lateral geniculate nucleus (LGN) and ... more The morphological and laminar characteristics of the dorsal lateral geniculate nucleus (LGN) and medial interlaminar nucleus (MIN) of the domestic dog (Canis familiaris) were studied by three-dimensional computer reconstruction of labeled retinal afferents following intraocular HRP injections. As previously reported, the dog LGN consisted of layers A, A1, C, C1, C2, and C3. Layers A, C, and C2 receive contralateral-eye inputs, and layers A1 and C1 ipsilateral inputs. The dog MIN was found to have four orderly interdigitating layers; layers 1, 2, 3, and 4, medial to lateral. MIN layers 1 and 3 received contralateral inputs, and layers 2 and 4 ipsilateral inputs. Layer 1 had the largest soma of all LGN/MIN layers. LGN layer A was partially separated into medial and lateral subdivisions by a cleft free of somata. The overall three-dimensional shape of the lateral geniculate body was like the letter C, with the convex part of the C directed posteriorly. The relative volume of the MIN was smaller than in the cat; the canine MIN comprised 8.3% of the combined volume of layers A, A1 and the MIN, while that of the cat comprised 14.2% as estimated from Sanderson&#39;s map. The volume of all contralateral-eye layers, combining both LGN and MIN, was 31.2 mm(3) (78%), and that for ipsilateral layers was 8.6 mm(3) (22%). The ratio of ipsilateral to contralateral laminar volumes is much lower in the dog than in the cat.
In this study, we examined functional contributions of major subdivisions of the lateral genicula... more In this study, we examined functional contributions of major subdivisions of the lateral geniculate nucleus to the cat's lateral suprasylvian visual area (LS) in relation to the patchy horizontal distributions of association inputs. Multiple-unit activity driven via the contralateral eye was assessed during reversible blockade of the retinotopically corresponding part of layer A, the C layers as a group, or the medial interlaminar nucleus (MIN). Inactivating each of these targets reduced activity at some cortical sites, with inactivation of layer A having, on average, the largest effect. Activity was rarely abolished by inactivation of a single target, indicating that most LS sites receive multiple inputs. Dependence on layer A was strongly correlated with the horizontal distribution of association inputs from area 18. Closely spaced injections of anatomical tracers into extensive regions of area 18 resulted in patches of terminal label in lateral suprasylvian cortex. Activity i...
The goal of this study was to determine the effects of inactivating layer A or the C layers of th... more The goal of this study was to determine the effects of inactivating layer A or the C layers of the cat lateral geniculate nucleus on the supragranular layers of area 18, including cells antidromically activated from the lateral suprasylvian visual area (LS). Isolated cells were visually driven via the contralateral eye while the retinotopically corresponding regions of layer A or, in some cases, the C layers were reversibly inactivated with injections of cobaltous chloride. Simple cells were frequently encountered and were on average more dependent upon layer A than were complex cells, a result qualitatively similar to that found previously in area 17 (Malpeli, 1983; Malpeli et al., 1986). However, the influence of the C layers on area 18 was much more apparent than for area 17. In area 18, as in area 17, the dependence of simple cells on particular geniculate layers appears to follow the terminal patterns of the major direct geniculate inputs. Those simple cells most dependent on l...
Uploads
Papers by Choongkil Lee