Biomedical subjects

J W Peirce

Publications and source records attributed to J W Peirce.

3 recordsLinked to original sources

PubMed2006

Selective mechanisms for complex visual patterns revealed by adaptation.

A great deal is known about the initial steps of visual processing. We know that humans have neural mechanisms selectively tuned to simple patterns of particular spatial frequencies and orientations. We also know that much later in the visual pathway, in inferotemporal cortex, cells respond to extremely complex visual patterns such as images of faces. Very little is known about intermediate levels of visual processing, where early visual signals are presumably combined to represent increasingly complex visual features. Here we show the existence of visual mechanisms in humans, tuned and selective to particular combinations of simple sinusoidal patterns, using a novel method of compound adaptation.

Acclimatization↗

PubMed2001

Sheep don't forget a face.

The human brain has evolved specialized neural mechanisms for visual recognition of faces, which afford us a remarkable ability to discriminate between, remember and think about many hundreds of different individuals. Sheep also recognize and are attracted to individual sheep and humans by their faces, as they possess similar specialized neural systems in the temporal and frontal lobes for assisting in this important social task, including a greater involvement of the right brain hemisphere. Here we show that individual sheep can remember 50 other different sheep faces for over 2 years, and that the specialized neural circuits involved maintain selective encoding of individual sheep and human faces even after long periods of separation.

Animals↗

PubMed2000

Configurational coding, familiarity and the right hemisphere advantage for face recognition in sheep.

This study examined characteristics of visual recognition of familiar and unfamiliar faces in sheep using a 2-way discrimination task. Of particular interest were effects of lateralisation and the differential use of internal (configurational) vs external features of the stimuli. Animals were trained in a Y-maze to identify target faces from pairs, both of which were familiar (same flock as the subjects) or both of which were unfamiliar (different flock). Having been trained to identify the rewarded face a series of stimuli were presented to the sheep, designed to test for the use of each visual hemifield in the discriminations and the use of internal and external facial cues. The first experiment showed that there was a left visual hemifield (LVF) advantage in the identification of 'hemifaces', and 'mirrored hemifaces' and 'chimeric' faces and that this effect was strongest with familiar faces. This represents the first evidence for visual field bias outside the primate literature. Results from the second experiment showed that, whilst both familiar and unfamiliar faces could be identified by the external features alone, only the familiar faces could be recognised by the internal features alone. Overall the results suggest separate recognition methods for socially familiar and unfamiliar faces, with the former being coded more by internal, configurational cues and showing a lateral bias to the left visual field.

Animals↗