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D I Perrett

Publications and source records attributed to D I Perrett.

66 records · Page 4Linked to original sources
PubMed1988

Characteristic views and the visual inspection of simple faceted and smooth objects: 'tetrahedra and potatoes'.

The way in which human subjects distribute their time when attempting to learn the surface appearance of objects placed on a stand free to rotate about its vertical axis was investigated. Experiments were undertaken to establish whether observers concentrate their time on particular views and, if so, to determine the image characteristics of the preferred views. For tetrahedra, subjects concentrated on views which presented a face or an edge centred on the line of sight. Both of these views were symmetric about the vertical axis. For potatoes as examples of opaque smooth objects, subjects concentrated on four views in which the object's principal (long) axis was oriented side-on or end-on to their line of sight. For such views the horizontal width (and surface area) of the object's image had maximum and minimum values. Preferred views were not systematically related to views defined as stable from the appearance of surface boundaries or 'singularities'.

Adult↗
PubMed1985

Visual cells in the temporal cortex sensitive to face view and gaze direction.

The direction of eye gaze and orientation of the face towards or away from another are important social signals for man and for macaque monkey. We have studied the effects of these signals in a region of the macaque temporal cortex where cells have been found to be responsive to the sight of faces. Of cells selectively responsive to the sight of the face or head but not to other objects (182 cells) 63% were sensitive to the orientation of the head. Different views of the head (full face, profile, back or top of the head, face rotated by 45 degrees up to the ceiling or down to the floor) maximally activated different classes of cell. All classes of cell, however, remained active as the preferred view was rotated isomorphically or was changed in size or distance. Isomorphic rotation by 90-180 degrees increased cell response latencies by 10-60 ms. Sensitivity to gaze direction was found for 64% of the cells tested that were tuned to head orientation. Eighteen cells most responsive to the full face preferred eye contact, while 18 cells tuned to the profile face preferred averted gaze. Sensitivity to gaze was thus compatible with, but could be independent of, sensitivity to head orientation. Results suggest that the recognition of one type of object may proceed via the independent high level analysis of several restricted views of the object (viewer-centred descriptions).

Animals↗
PubMed1985

A technique for microiontophoretic study of single neurones in the behaving monkey.

A technique is described for the construction and use of iontophoretic electrodes suitable for extracellular single-unit work in awake behaving monkeys. The technique combines a multi-barrelled pipette for iontophoresis and an insulated tungsten electrode that is employed routinely for chronic single-unit recordings. The pipette consists of up to 11 double filamented glass barrels concentrically arranged around a large diameter glass tube. The recording electrode is extruded through the central tube under microscopic control and glued in place. This technique allows separate optimization of the shape of the recording electrode for recording in the behaving monkey, and of the iontophoretic tips. An adapted micropositioner is used to accommodate the electrode's unusual length, required in order to allow access to deep brain structures and so that a guide tube can protect the trans-dural passage of the electrode tip.

Animals↗
PubMed1985

Visual analysis of body movements by neurones in the temporal cortex of the macaque monkey: a preliminary report.

Movement provides biologically important information about the nature (and intent) of animate objects. We have studied cells in the superior temporal sulcus of the macaque monkey which seem to process such visual information. We found that the majority of cells in this brain region were selective for type of movement and for stimulus form, most cells responding only to particular movements of the body or some part of it. A variety of cell types emerged, including cells sensitive to: translation of bodies in view, movements into view (appearance) or out of view (disappearance) and the articulation and rotation of the body/head. Directional selectivity for cells sensitive to translation tended to lie along one of 3 orthogonal Cartesian axes centred on the monkey (towards/away, left/right and up/down). One type of rotation sensitive cell was tuned to rotation about one or more of these axes, a second type was sensitive to different head rotations which brought the face to confront the monkey or turned the face away. Reconstructions of cell positions indicated that cells of the same type were clumped anatomically both across the surface of the cortex and perpendicular to the surface.

Animals↗
PubMed1984

Responses of striatal neurons in the behaving monkey. 2. Visual processing in the caudal neostriatum.

The activity of single neurons was recorded in the tail of the caudate nucleus and adjoining part of the ventral putamen, which receive projections from the inferior temporal visual cortex, in order to investigate the functions of these regions. Of 195 neurons analyzed in two macaque monkeys, 109 (56%) responded to visual stimuli, with latencies of 90-150 ms for the majority of the neurons. The neurons responded to a limited range of complex visual stimuli, and in some cases responded to simpler stimuli such as bars and edges. Typically (in 75% of cases) the neurons habituated rapidly, within 1-8 exposures, to each visual stimulus, but remained responsive to other visual stimuli with a different pattern. This habituation was orientation specific, in that the neurons responded to the same pattern shown in an orthogonal orientation. The habituation was also relatively short-term, in that at least partial dishabituation to one stimulus could be produced by a single intervening presentation of a different visual stimulus. These neurons were relatively unresponsive in a visual discrimination task, having habituated to the stimuli which had been presented in the task on many previous trials. It is suggested on the basis of these results and other studies that these neurons are involved in pattern-specific habituation to repeated visual stimuli, and in attention an orientation to a changed visual stimulus pattern. Changes in attention and orientation to stimuli as a result of damage to the striatum and its afferent and efferent pathways may arise in part because of damage to neurons with responses of this type.

Animals↗
PubMed1984

Responses of striatal neurons in the behaving monkey. 3. Effects of iontophoretically applied dopamine on normal responsiveness.

In order to analyse the functions of dopamine, the effects of the iontophoretic application of dopamine on the responsiveness of striatal neurons to their normal inputs were investigated in the behaving monkey. It was shown that many neurons in the putamen had responses related to movements, of for example the mouth. Iontophoretically applied dopamine decreased the spontaneous firing rates of 178 of 267 neurons (67%) tested in the putamen, caudate nucleus, and the adjacent prefrontal cortex which also receives a dopaminergic projection. Trifluoperazine, applied iontophoretically to block dopamine receptors, increased the spontaneous firing rates of some of the neurons in the prefrontal cortex, suggesting that under normal conditions in the behaving animal the release of dopamine holds the firing rates of these neurons at a low level. The median was 9 spikes/s in the present sample of striatal neurons. Application of dopamine decreased the magnitude of the movement-related responses of the striatal neurons; this decrease in the responses was of approximately the same magnitude in spikes per second as the decrease in the spontaneous firing rate of the neurons produced by the same current of dopamine. It is suggested that this type of effect of dopamine could influence the signal to noise ratio of processing within the striatum, and that changes in this signal to noise ratio produced by disturbances of dopaminergic function could contribute to the behavioral disorders produced by dysfunctions of the dopaminergic systems.

Animals↗
PubMed1984

Neurones responsive to faces in the temporal cortex: studies of functional organization, sensitivity to identity and relation to perception.

We have investigated the distribution of cells responsive to faces within the macaque temporal cortex and their sensitivity to different face attributes. We found a functional organization of cells responsive to the sight of different views of the head. Cells of a similar type were grouped together both vertically down through the cortex, and horizontally in patches extending 0.5-2.0 mm across the surface of the cortex. A substantial proportion of cells responsive to faces were found to be sensitive to biologically important characteristics such as identity or expression. Cells were found to be highly selective for particular individuals that were familiar to the monkey with selectivity persisting across a great variety of viewing conditions such as changing face expression, orientation, colour, distance and size. Data suggested that sensitivity to identity arises at the level of specific views of the individual (e.g. full face). Information about different views may then be pooled to allow recognition independent of view. Visual transformations that make it difficult for humans to perceive faces (e.g., contrast reversal, isoluminant colour, coarsely quantized images, rotation or inversion) reduced the magnitude or increased the latency of cells' responses to faces. In this way, cell responses were related to perception and not simply to visual qualities of the image.

Adolescent↗
PubMed1982

Visual neurones responsive to faces in the monkey temporal cortex.

Of 497 single neurones recorded in the cortex in the fundus of the superior temporal sulcus (STS) of three alert rhesus monkeys, a population of at least 48 cells which were selectively responsive to faces had the following response properties: (1) The cells' responses to faces (real or projected, human or rhesus monkey) were two to ten times as large as those to gratings, simple geometrical stimuli or complex 3-D objects. (2) Neuronal responses to faces were excitatory, sustained and were time-locked to the stimulus presentation with a latency of between 80 and 160 ms. (3) The cells were unresponsive to auditory or tactile stimuli and to the sight of arousing or aversive stimuli. (4) The magnitude of the responses of 28 cells tested was relatively constant despite transformations, such as rotation, so that the face was inverted or horizontal, and alterations of colour, size or distance. (5) Rotation to profile substantially reduced the responses of 21 cells (31 tested). (6) Masking out or presenting parts of the face (i.e. eyes, mouth or hair) in isolation revealed that different cells responded to different features or subsets of features. (7) For several cells, responses to the normal organisation of cut-out or line-drawn facial features were significantly larger than to jumbled controls. These findings indicate that explanations in terms of arousal, emotional or motor reactions, simple visual feature sensitivity or receptive fields are insufficient to account for the selective responses to faces and face features observed in this population of STS neurones. It appears that these neurones are part of a system specialised to code for faces or features present in faces, and it is suggested that damage to this system is related to prosopagnosia, or difficulty in face recognition, in man and to the tameness and social disturbances which follow temporal lobe damage and are part of the Klüver-Bucy syndrome in the monkey.

Animals↗
PubMed1982

Neuronal responses related to visual recognition.

To analyse the neural basis of long-term memory, recordings were made from single neurons in monkeys performing a visual recognition task of the type impaired in anterograde amnesia in man. Each visual stimulus was shown twice per day, once as novel, and after 0 to 17 other intervening items in the recognition task, on a second trial, as familiar, when the monkey could lick to obtain fruit juice if he recognized the stimulus correctly. At the anterior border of the thalamus, a population of neurons was found which responded to the stimuli only when they were familiar. The activity of these neurons was not related to lick responses. Further, in a different, visual discrimination, task, a number of these neurons were found to respond both to the familiar rewarded stimulus to which the monkey always licked, and to the familiar aversive stimulus to which he did not lick. This shows that in a reward association task these neurons respond on the basis of familiarity, providing evidence for a dissociation of recognition and associative memories. Analysis of the responses of these neurons in the continuous visual recognition task showed that the responses to familiar stimuli were time-locked to the onset and duration of the visual stimulation (brief exposures producing brief responses). The response latencies were in the range 100 to 200 ms. A 100 ms exposure of the stimulus was sufficient for the stimulus to be encoded, and a 100 ms exposure was also sufficient for a recognition related response. The magnitude of the neuronal response on trials with familiar stimuli decreased as the number of trials between the first (novel) and second (familiar) presentation of the same stimulus increased. The rate of this decay or 'forgetting' varied from cell to cell and was best described by an exponential function. Repeated exposure tended to slow the rate of forgetting, and two or three repeated presentations prolonged some cell 'memories' for more than 100 intervening trials. Although the majority of the neurons did not have such long 'memories', in that they responded as novel to stimuli seen on a preceding day, so that their responses could be related to recency but not to absolute recognition of ever having seen a stimulus before, 2 neurons did respond to stimuli which had not been seen for 24 h. The neurons showed some ability to respond to stimuli as familiar despite changes in viewing conditions and transformations such as 90 deg rotation. These findings indicate that the responses of these neurons at the anterior border of the thalamus are activated during recency or longer term recognition processing, both of which are impaired in anterograde amnesia in man. Measurement of the responses of these neurons, which appear to have access to memory mechanisms, has allowed parameters affecting such memory mechanisms to be investigated.

Amnesia↗
PubMedDate not supplied

Recognition of objects and their component parts: responses of single units in the temporal cortex of the macaque.

We investigated the role that different component parts play in the neural encoding of the visual appearance of one complex object in the temporal cortex. Cells responsive to the sight of the entire human body (but no to control stimuli) were tested with two subregions (head alone with the body occluded from sight and the body alone with the head occluded). Forty-two percent (22 of 53) of cells responded to the whole body and to one of the two body regions tested separately: 72% (17 of 22) responding to the head and 28% (5 of 22) to the rest of the body. Forty-two percent (22 of 53) of cells responded independently to both regions of the body when tested in isolation. The remaining cells (17%, 9 of 53) were selective for the entire body and unresponsive to component parts. The majority of cells tested (90%, 35 of 39) were selective for perspective view (e.g., some cells respond optimally to the side view of the body, others to the back view). Comparable levels of view sensitivity were found for responses to the whole body and its parts. Results indicate (1) separate neuronal analysis of body parts and (2) extensive integration of information from different parts. Contrary to influential models of object recognition (Marr and Nishihara, 1978; Biederman, 1987), the results indicate view-specific processing both for the appearance of separate object components and for integration of information across components.

Animals↗
PubMedDate not supplied

Visual recognition based on temporal cortex cells: viewer-centred processing of pattern configuration.

A model of recognition is described based on cell properties in the ventral cortical stream of visual processing in the primate brain. At a critical intermediate stage in this system, 'Elaborate' feature sensitive cells respond selectively to visual features in a way that depends on size (+/- 1 octave), orientation (+/- 45 degrees) but does not depend on position within central vision (+/- 5 degrees). These features are simple conjunctions of 2-D elements (e.g. a horizontal dark area above a dark smoothly convex area). They can arise either as elements of an object's surface pattern or as a 3-D component bounded by an object's external contour. By requiring a combination of several such features without regard to their position within the central region of the visual image, 'Pattern' sensitive cells at higher levels can exhibit selectivity for complex configurations that typify objects seen under particular viewing conditions. Given that input features to such Pattern sensitive cells are specified in approximate size and orientation, initial cellular 'representations' of the visual appearance of object type (or object example) are also selective for orientation and size. At this level, sensitivity to object view (+/- 60 degrees) arises because visual features disappear as objects are rotated in perspective. Processing is thus viewer-centred and the neurones only respond to objects seen from particular viewing conditions or 'object instances'. Combined sensitivity to multiple features (conjunctions of elements) independent of their position, establishes selectivity for the configurations of object parts (from one view) because rearranged configurations of the same parts yield images lacking some of the 2-D visual features present in the normal configuration. Different neural populations appear to be selectively tuned to particular components of the same biological object (e.g. face, eyes, hands, legs), perhaps because the independent articulation of these components gives rise to correlated activity in different sets of input visual features. Generalisation over viewing conditions for a given object can be established by hierarchically pooling outputs of view-condition specific cells with pooling operations dependent on the continuity in experience across viewing conditions. Different object parts are seen together and different views are seen in succession when the observer walks around the object. The view specific coding that characterises the selectivity of cells in the temporal lobe can be seen as a natural consequence of selective experience of objects from particular vantage points. View specific coding for the face and body also has great utility in understanding complex social signals, a property that may not be feasible with object-centred processing.

Animals↗