FIGURE 1

Schematic summary of auditory cortical circuits and alterations observed in subjects with schizophrenia. Auditory sensory processing is primarily initiated via projections (red) from the ventral subdivision of the medial geniculate nucleus of the thalamus to layers 4 and 3c of BA 41, the primary auditory (core) cortex (Pandya et al, 1994; Pandya and Rosene, 1993; Molinari et al, 1995; Hashikawa et al, 1995). Excitation within the core spreads through layer 3 via ascending projections from layer 4 (black) and axon collaterals from layer 3 (thin green) pyramidal cells, synapsing predominantly onto dendritic spines of layer 3 pyramidal cells (Mitani et al, 1985; Ojima et al, 1991; Wallace et al, 1991; Lee et al, 2004; Watts and Thomson, 2005). Feedforward projections from core to lateral belt (thick green) arise predominantly from layer 3 pyramidal cells (Pandya and Sanides, 1973; Jones et al, 1995; Galaburda and Pandya, 1983; Fitzpatrick and Imig, 1980). Feedback projections (blue) from lateral belt arise predominantly from layer 5 and terminate in layer 1 of core (Jones et al, 1995; Galaburda and Pandya, 1983; Pandya and Sanides, 1973; Pandya and Rosene, 1993). The same arrangement of feedforward and feedback projections exists between lateral belt and parabelt (not shown), which together consist BA 42. Layers assessed in earlier studies of subjects with schizophrenia are indicated by the dashed lines, with findings summarized as shown. MGN_V, ventral subdivision of the medial geniculate nucleus; MGN_D, dorsal subdivision of the medial geniculate nucleus.