Macaque monkeys were presented with continuous rapid serial visual presentation (RSVP) sequences of unrelated naturalistic images at rates of 14-222 msec/image, while neurons that responded selectively to complex patterns (e.g., faces) were recorded in temporal cortex. Stimulus selectivity was preserved for 65% of these neurons even at surprisingly fast presentation rates (14 msec/image or 72 images/sec). Five human subjects were asked to detect or remember images under equivalent conditions. Their performance in both tasks was above chance at all rates (14-111 msec/image). The performance of single neurons was comparable to that of humans and responded in a similar way to changes in presentation rate. The implications for the role of temporal cortex cells in perception are discussed.

Cells have been found in the superior temporal polysensory area (STPa) of the macaque temporal cortex that are selectively responsive to the sight of particular whole body movements (e.g., walking) under normal lighting. These cells typically discriminate the direction of walking and the view of the body (e.g., left profile walking left). We investigated the extent to which these cells are responsive under “biological motion” conditions where the form of the body is defined only by the movement of light patches attached to the points of limb articulation. One-third of the cells (25/72) selective for the form and motion of walking bodies showed sensitivity to the moving light displays. Seven of these cells showed only partial sensitivity to form from motion, in so far as the cells responded more to moving light displays than to moving controls but failed to discriminate body view. These seven cells exhibited directional selectivity. Eighteen cells showed statistical discrimination for both direction of movement and body view under biological motion conditions. Most of these cells showed reduced responses to the impoverished moving light stimuli compared to full light conditions. The 18 cells were thus sensitive to detailed form information (body view) from the pattern of articulating motion. Cellular processing of the global pattern of articulation was indicated by the observations that none of these cells were found sensitive to movement of individual limbs and that jumbling the pattern of moving limbs reduced response magnitude. A further 10 cells were tested for sensitivity to moving light displays of whole body actions other than walking. Of these cells 5/10 showed selectivity for form displayed by biological motion stimuli that paralleled the selectivity under normal lighting conditions. The cell responses thus provide direct evidence for neural mechanisms computing form from nonrigid motion. The selectivity of the cells was for body view, specific direction, and specific type of body motion presented by moving light displays and is not predicted by many current computational approaches to the extraction of form from motion.

We have previously reported that a patient (DF) with visual form agnosia shows accurate guidance of hand and finger movements with respect to the size, orientation, and shape of the objects to which her movements are directed. Despite this, she is unable to indicate any knowledge about these object properties. In the present study, we investigated the extent to which DF is able to use visual shape or pattern to guide her hand movements. In the first experiment, we found that when presented with a stimulus aperture cut in the shape of the letter T, DF was able to guide a T-shaped form into it on about half of the trials, across a range of different stimulus orientations. On the remaining trials, her responses were almost always perpendicular to the correct Orientation. Thus, the visual information guiding the rotation of DF's hand appears to be limited to a single orientation. In other words, the visuomotor transformations mediating her hand rotation appear to be unable to combine the orientations of the stem and the top of the T, although they are sensitive to the orientation of the element(s) that comprise the T. In a second experiment, we examined her ability to use different sources of visual information to guide her hand rotation. In this experiment, DF was required to guide the leading edge of a hand-held card onto a rectangular target positioned at dHerent orientations on a flat surface. Here the orientation of her hand was determined primarily by the predominant orientation of the luminance edge elements present in the stimulus, rather than by information about orientation that was conveyed by nonluminance boundaries. Little evidence was found for an ability to use contour boundaries defined by Gestalt principles of grouping (good continuation or similarity) or “nonaccidental” image properties (colinearity) to guide her movements. We have argued elsewhere that the dorsal visual pathway from occipital to parietal cortex may underlie these preserved visuomotor skills in DF. If so, the limitations in her ability to use different kinds of “pattern” information to guide her hand rotation suggest that such information may need to be transmitted from the ventral visual stream to these parietal areas to enable the full range of prehensive acts in the intact individual.

Physiological recordings along the length of the upper bank of the superior temporal sulcus (STS) revealed cells each of which was selectively responsive to a particular view of the head and body. Such cells were grouped in large patches 3-4 mm across. The patches were separated by regions of cortex containing cells responsive to other stimuli. The distribution of cells projecting from temporal cortex to the posterior regions of the inferior parietal lobe was studied with retrogradely transported fluorescent dyes. A strong temporoparietal projection was found originating from the upper bank of the STS. Cells projecting to the parietal cortex occurred in large patches or bands. The size and periodicity of modules defined through anatomical connections matched the functional subdivisions of the STS cortex involved in face processing evident in physiological recordings. It is speculated that the temporoparietal projections could provide a route through which temporal lobe analysis of facial signals about the direction of others' attention can be passed to parietal systems concerned with spatial awareness.