Papers by Robert Robertson
The spatio-temporal properties of saccadic eye movements can be influenced by the cognitive deman... more The spatio-temporal properties of saccadic eye movements can be influenced by the cognitive demand and the characteristics of the observed scene. Probably due to its crucial role in social communication, it is argued that face perception may involve different cognitive processes compared with non-face object or scene perception. In this study, we investigated whether and how face and natural scene images can influence the patterns of visuomotor activity. We recorded monkeys’ saccadic eye movements as they freely viewed monkey face and natural scene images. The face and natural scene images attracted similar number of fixations, but viewing of faces was accompanied by longer fixations compared with natural scenes. These longer fixations were dependent on the context of facial features. The duration of fixations directed at facial contours decreased when the face images were scrambled, and increased at the later stage of normal face viewing. The results suggest that face and natural s...
Centre-surround interaction in the primary visual cortex (area V1) has been studied extensively u... more Centre-surround interaction in the primary visual cortex (area V1) has been studied extensively using artificial, abstract stimulus patterns, such as bars, gratings and simple texture patterns. In this experiment, we extend the study of centre-surround interaction by using natural scene images. We systematically varied the contrast of natural image surrounds presented outside the classical receptive field (CRF), and recorded neuronal response to a natural image patch presented within the CRF in area V1 of awake, fixating macaques. For the majority of neurons (67 out of 111), the natural image surrounds profoundly modulated, mainly by suppressing, neuronal responses to CRF images. These modulatory effects started at the earliest stage of neuronal responses, and often depended on the contrast and higher-order structures of the surrounds. For 47 out of 67 neurons, randomising the phases of the Fourier spectrum of the natural image surround diminished the centre-surround interaction. Our results suggest that the centresurround interaction in area V1 can be extended to natural vision, and is sensitive to the higher-order structures of natural scene images, such as image contours.
Journal of Neurophysiology, 1998
Rolls, Edmund T., Alessandro Treves, Robert G. Robertson, Pierre Georges-François, and Stefano Pa... more Rolls, Edmund T., Alessandro Treves, Robert G. Robertson, Pierre Georges-François, and Stefano Panzeri. Information about spatial view in an ensemble of primate hippocampal cells. J. Neurophysiol. 79: 1797–1813, 1998. Hippocampal function was analyzed by making recordings from hippocampal neurons in monkeys actively walking in the laboratory. “Spatial view” cells, which respond when the monkey looks at a part of the environment, were analyzed. To assess quantitatively the information about the spatial environment represented by these cells, we applied information theoretic techniques to their responses. The average information provided by these cells about which location the monkey was looking at was 0.32 bits, and the mean across cells of the maximum information conveyed about which location was being looked at was 1.19 bits, measured in a period of 0.5 s. There were 16 locations for this analysis, each being one-quarter of one of the walls of the room. It also was shown that the m...
Journal of Neurophysiology, 2004
Recent in vitro studies have shown that acetylcholine (ACh) selectively reduces the efficacy of l... more Recent in vitro studies have shown that acetylcholine (ACh) selectively reduces the efficacy of lateral cortical connections via a muscarinic mechanism, while boosting the efficacy of thalamocortical/feed-forward connections via a nicotinic mechanism. This suggests that high levels of ACh should reduce center-surround interactions of neurons in primary visual cortex, making cells more reliant on feed-forward information. In line with this hypothesis, we show that local iontophoretic application of ACh in primate primary visual cortex reduced the extent of spatial integration, assessed by recording a neurons' length tuning. When ACh was externally applied, neurons' preferred length shifted toward shorter bars, showing reduced impact of the extra-classical receptive field. We fitted a difference and a ratio of Gaussian model to these data to determine the underlying mechanisms of this dynamic change of spatial integration. These models assume overlapping summation and suppress...
Experimental brain research, 2003
Face perception plays a crucial role in primate social communication. We have investigated the pa... more Face perception plays a crucial role in primate social communication. We have investigated the pattern of eye movements produced by rhesus monkeys (Macaca mulatta) as they viewed images of faces. Eye positions were recorded accurately using implanted eye coils, while neutral upright, inverted and scrambled images of monkey and human faces were presented on a computer screen. The monkeys exhibited a similar eye scan pattern while viewing familiar and unfamiliar monkey face images, or while viewing monkey and human face images. No differences were observed in the distribution of viewing times, number of fixations, time into the trial of first saccade to local facial features, and the temporal and spatial characteristics of viewing patterns across the facial images. However, there was a greater probability of re-fixation of the eye region of unfamiliar faces during the first few seconds of the trial suggesting that the eyes are important for the initial encoding of identity. Indeed, th...
Neuroscience, 2006
It is traditional to believe that neurons in primary visual cortex are sensitive only or principa... more It is traditional to believe that neurons in primary visual cortex are sensitive only or principally to stimulation within a spatially restricted receptive field (classical receptive field). It follows from this that they should only be capable of encoding the direction of stimulus movement orthogonal to the local contour, since this is the only information available in their classical receptive field "aperture." This direction is not necessarily the same as the motion of the entire object, as the direction cue within an aperture is ambiguous to the global direction of motion, which can only be derived by integrating with unambiguous components of the object. Recent results, however, show that primary visual cortex neurons can integrate spatially and temporally distributed cues outside the classical receptive field, and so we reexamined whether primary visual cortex neurons suffer the "aperture problem." With the stimulation of an optimally oriented bar drifting across the classical receptive field in different global directions, here we show that a subpopulation of primary visual cortex neurons (25/81) recorded from anesthetized and paralyzed marmosets is capable of integrating informative unambiguous direction cues presented by the bar ends, well outside their classical receptive fields, to encode global motion direction. Although the stimuli within the classical receptive field were identical, their directional responses were significantly modulated according to the global direction of stimulus movement. Hence, some primary visual cortex neurons are not local motion energy filters, but may encode signals that contribute directly to global motion processing.
Experimental Brain Research, 2005
The spatio-temporal properties of saccadic eye movements can be influenced by the cognitive deman... more The spatio-temporal properties of saccadic eye movements can be influenced by the cognitive demand and the characteristics of the observed scene. Probably due to its crucial role in social communication, it is argued that face perception may involve different cognitive processes compared with non-face object or scene perception. In this study, we investigated whether and how face and natural scene images can influence the patterns of visuomotor activity. We recorded monkeys' saccadic eye movements as they freely viewed monkey face and natural scene images. The face and natural scene images attracted similar number of fixations, but viewing of faces was accompanied by longer fixations compared with natural scenes. These longer fixations were dependent on the context of facial features. The duration of fixations directed at facial contours decreased when the face images were scrambled, and increased at the later stage of normal face viewing. The results suggest that face and natural scene images can generate different patterns of visuomotor activity. The extra fixation duration on faces may be correlated with the detailed analysis of facial features.
European Journal of Neuroscience, 2005
Centre-surround interaction in the primary visual cortex (area V1) has been studied extensively u... more Centre-surround interaction in the primary visual cortex (area V1) has been studied extensively using artificial, abstract stimulus patterns, such as bars, gratings and simple texture patterns. In this experiment, we extend the study of centre-surround interaction by using natural scene images. We systematically varied the contrast of natural image surrounds presented outside the classical receptive field (CRF), and recorded neuronal response to a natural image patch presented within the CRF in area V1 of awake, fixating macaques. For the majority of neurons (67 out of 111), the natural image surrounds profoundly modulated, mainly by suppressing, neuronal responses to CRF images. These modulatory effects started at the earliest stage of neuronal responses, and often depended on the contrast and higher-order structures of the surrounds. For 47 out of 67 neurons, randomising the phases of the Fourier spectrum of the natural image surround diminished the centre-surround interaction. Our results suggest that the centresurround interaction in area V1 can be extended to natural vision, and is sensitive to the higher-order structures of natural scene images, such as image contours.
Hippocampus, 1999
The function of the primate hippocampus and related structures was analysed by making recordings ... more The function of the primate hippocampus and related structures was analysed by making recordings from the hippocampus, subiculum, presubiculum, and parahippocampal gyrus in monkeys actively walking in the laboratory. Head direction cells were found in the presubiculum. The firing rate of these cells was a function of the head direction of the monkey, with a response that was typically 10-100 times larger to the best as compared to the opposite direction. The mean half-amplitude width of the tuning of the cells was 76°. The response of head direction cells in the presubiculum was not influenced by the place where the monkey was, there being the same tuning to head direction at different places in a room, and even outside the room. The response of these cells was also independent of the ''spatial view'' observed by the monkey, and also the position of the eyes in the head. The average information about head direction was 0.64 bits, about place was 0.10 bits, about spatial view was 0.27 bits, and about eye position was 0.04 bits. The cells maintained their tuning for periods of at least several minutes when the view details were obscured or the room was darkened. This representation of head direction could be useful together with the hippocampal spatial view cells and whole body motion cells found in primates in such spatial and memory functions as path integration.
European Journal …, 2006
Cortical processing is strongly influenced by the actions of neuromodulators such as acetylcholin... more Cortical processing is strongly influenced by the actions of neuromodulators such as acetylcholine (ACh). Early studies in anaesthetized cats argued that acetylcholine can cause a sharpening of orientation tuning functions and an improvement of the signal-to-noise ratio (SNR) of ...
Journal of …, 1998
Robertson, Robert G., Edmund T. Rolls, and Pierre Georgeskeys perform object-place memory tasks i... more Robertson, Robert G., Edmund T. Rolls, and Pierre Georgeskeys perform object-place memory tasks in which they must François. Spatial view cells in the primate hippocampus: effects remember where on a video monitor a picture has been of removal of view details.
European Journal of …, 1997
Robertson, Robert G., Edmund T. Rolls, and Pierre Georgeskeys perform object-place memory tasks i... more Robertson, Robert G., Edmund T. Rolls, and Pierre Georgeskeys perform object-place memory tasks in which they must François. Spatial view cells in the primate hippocampus: effects remember where on a video monitor a picture has been of removal of view details.
Cerebral Cortex, 1999
Hippocampal function was analysed by making recordings from hippocampal neurons in monkeys active... more Hippocampal function was analysed by making recordings from hippocampal neurons in monkeys actively walking in the laboratory. 'Spatial view' cells, which respond when the monkey looks at a part of the environment, were analysed. It is shown that these cells code for the ...
European Journal of Neuroscience, Aug 1, 2007
In normal vision, visual scenes are predictable, as they are both spatially and temporally redund... more In normal vision, visual scenes are predictable, as they are both spatially and temporally redundant. Evidence suggests that the visual system may use the spatio-temporal regularities of the external world, available in the retinal signal, to extract information from the visual environment and better reconstruct current and future stimuli. We studied this by recording neuronal responses of primary visual cortex (area V1) in anaesthetized and paralysed macaques during the presentation of dynamic sequences of ...
Journal of …, 1998
Rolls, Edmund T., Alessandro Treves, Robert G. Robertson, Pierre Georges-François, and Stefano Pa... more Rolls, Edmund T., Alessandro Treves, Robert G. Robertson, Pierre Georges-François, and Stefano Panzeri. Information about spatial view in an ensemble of primate hippocampal cells. J. Neurophysiol. 79: 1797–1813, 1998. Hippocampal function was analyzed by making recordings from hippocampal neurons in monkeys actively walking in the laboratory.“Spatial view” cells, which respond when the monkey looks at a part of the environment, were analyzed. To assess quantitatively the information about the spatial ...
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Papers by Robert Robertson