Studies of cortical connections or neuronal function in different cerebral areas support the hypothesis that parallel cortical processing streams, similar to those identified in visual cortex, may exist in the auditory system. However, this model has not yet been behaviorally tested. We used reversible cooling deactivation to investigate whether the individual regions in cat nonprimary auditory cortex that are responsible for processing the pattern of an acoustic stimulus or localizing a sound in space could be doubly dissociated in the same animal. We found that bilateral deactivation of the posterior auditory field resulted in deficits in a sound-localization task, whereas bilateral deactivation of the anterior auditory field resulted in deficits in a pattern-discrimination task, but not vice versa. These findings support a model of cortical organization that proposes that identifying an acoustic stimulus ('what') and its spatial location ('where') are processed in separate streams in auditory cortex.
Legend: The effects of cooling posterior and anterior regions of auditory cortex are doubly disassociated, with anterior regions being important for discriminating between sounds and posterior parts being important for localizing them.
Thursday, May 29, 2008
What and Where pathways in auditory brain
The visual cortex has parallel processing streams that deal mainly either with the location of an image (the dorsal stream) or its identity (the ventral stream). It now appears that auditory cortex (in cats) has similar parallel processing of the location and identity of sounds. Here is the abstract from Lomber and Malhotra and a graphic from the summary by Sumner and Moore.