Neuronal responses found in different temporal lobe cortex visual areas

While recording in the temporal lobe cortical visual areas of macaques, Charles Gross and colleagues found some neurons that appeared to respond best to complex visual stimuli such as faces (Bruce et al., 1981; Desimone and Gross, 1979; see also Desimone, 1991). It was soon found that while some of these neurons could respond to parts of faces, other neurons required several parts of the face to be present in the correct spatial arrangement, and that many of these neurons did not just respond to any face that was shown, but responded differently to different faces (Desimone et al., 1984; Gross et al., 1985; Perrett et al., 1982; Rolls, 1984). By responding differently to different faces, these neurons potentially encode information useful for identifying individual faces. This early work showed that there is some specialization of function of different temporal cortical visual areas, and this specialization of function is described next.

The visual pathways project from the primary visual cortex V1 to the temporal lobe visual cortical areas by a number of intervening ventral stream cortical stages including V2 and V4 (Baizer et al., 1991; Rolls and Deco, 2002; Seltzer and Pandya, 1978). The inferior temporal visual cortex, area TE, is divided on the basis of cytoarchitecture, myeloarchitecture, and afferent input into areas TEa, TEm, TE3, TE2, and TE1. In addition, there is a set of different areas in the cortex in the superior temporal sulcus (Baylis et al., 1987; Seltzer and Pandya, 1978) (Fig. 78.1). Of these latter areas, TPO receives inputs from temporal, parietal, and occipital cortex; PGa and IPa from parietal and temporal cortex; and TS and TAa primarily from auditory areas (Seltzer and Pandya, 1978).

Figure 78.1..  

Lateral view of the macaque brain showing the different architectonic areas (e.g., TEm, TPO) in and bordering the anterior part of the superior temporal sulcus of the macaque (see text).

There is considerable specialization of function in these architectonically defined areas (Baylis et al., 1987). Areas TPO, Pga, and IPa are multimodal, with neurons that respond to visual, auditory, and/or somatosensory inputs. The more ventral areas in the inferior temporal gyrus (areas TE3, TE2, TE1, TEa, and TEm) are primarily unimodal visual areas. Areas in the cortex in the anterior and dorsal part of the superior temporal sulcus (e.g., TPO, IPa, and IPg) have neurons specialized for the analysis of moving visual stimuli. Neurons responsive primarily to faces are found more frequently in areas TPO, TEa, and TEm, where they comprise approximately 20% of the visual neurons responsive to stationary stimuli, in contrast to the other temporal cortical areas, in which they comprise 4% to 10%. The stimuli which activate other cells in these TE regions include simple visual patterns such as gratings and combinations of simple stimulus features (Baylis et al., 1987; Gross et al., 1985; Tanaka et al., 1990). Neurons with responses related to facial expression, movement, and gesture are more likely to be found in the cortex in the superior temporal sulcus, whereas neurons with activity related to facial identity are more likely to be found in the TE areas (see below and Hasselmo et al., 1989a).