The representation of sound frequency (and of the cochlear partition) within primary auditory cortex has been investigated with use of microelectrode-mapping techniques in a series of 25 anesthetized cats. Among the results were the following: 1) Within vertical penetrations into AI, best frequency and remarkably constant for successively studied neurons across the active middle and deep cortical layers. 2) There is an orderly representation of frequency (and of represented cochlear place) within AI. Frequency is rerepresented across the mediolateral dimension of the field. On an axis perpendicular to this plane of rerepresentation, best-frequency (represented cochlear place) changes as a simple function of cortical location. 3) Any given frequency band (or sector of the cochlear partition) is represented across a belt of cortex of nearly constant width that runs on a nearly straight axis across AI. 4) There is a disproportionately large cortical surface representation of the highest-frequency octaves (basal cochlea) within AI. 5) The primary and secondary field locations were somewhat variable, when referenced to cortical surface landmarks. 6) Data from long penetrations passing down the rostral bank of the posterior ectosylvian sulcus were consistent with the existence of a vertical unit of organization in AI, akin to cortical columns described in primary visual and somatosensory cortex. 7) Responses to tonal stimuli were encountered in fields dorsocaudal, caudal, ventral, and rostral to AI. There is an orderly representation of the cochlea within the field rostal to AI, with a reversal in best frequencies across its border with AI. 8) Physiological definitions of AI boundaries are consistent with their cytoarchitectonic definition. Some of the implications of these findings are discussed.

The thalamocortical and corticothalamic connections of the three cortical auditory fields -first (AI), second (AII), and anterior (AAF)-were defined using anterograde and retrograde tracing techniques. Microinjections of tracers were placed a t one or two different physiologically identified loci after these fields had been mapped using microelectrode recording techniques. This approach ensured that the injections were well within the borders of each field that was studied. By making injections at different positions in the cochleotopic representations in A1 and AAF the systematic topographies of the connections between these cortical fields and the medial geniculate body subdivisions were determined.The thalamocortical and corticothalamic reciprocal projections of single loci in A1 were from and to single columns passing rostrocaudally through the deep dorsal nucleus (Dd) and medial division (M) of the medial geniculate body (MGB) and from and to folded sheets of labelled neurons passing rostrocaudally through pars lateralis (Vl) and pars ovoidea (Vo) of the ventral division. The connections of A1 with V1 and Vo were very strong. There were also thalamocortical and corticothalamic connections between the lateral division of the posterior group of thalamus (Pol) and single loci in AI.The thalamocortical and corticothalamic reciprocal connections of AAF with the auditory thalamus were similar to the A1 connections with the exception that the connections with the ventral division of the MGB were relatively weaker and, in the case of the thalamocortical projection, more discontinuous.A11 loci are thalamocortically and corticothalamically connected with the caudal dorsal nucleus (Dc), the ventral lateral nucleus (VL), and the medial division (MI.The topography of all connections of AAF and A1 with the MGB varied systematically and was consistent with a cochleotopic organization of connections between the MGB and the two cortical fields.Since the thalamocortical and corticothalamic connections of these three cortical fields are reciprocal, we were able to compare directly their connections in individual cats by introducing anterograde tracer in one field and retrograde tracer in another. While A1 and AAF were connected to the same subdivisions of the MGB and had the same systematic topography of connections, the connections of A11 and A1 (or AAF) were largely segregated (with the only

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Laboratory research has established that face recognition memory performance for ownrace faces is better than for other-race faces. Three studies are reported exploring the possibility that the other-race effect will generalize to voice recognition memory. Recognition memory performance for non-native American speakers speaking both English and their native languages was compared with memory for native American speakers. With relatively long speech samples, accented voices were no more difficult to recognize than were unaccented voices; reducing the speech sample duration decreased recognition memory for accented and unaccented voices, but the reduction was greater for accented voices.

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