Auditory event-related potentials (ERPs) were recorded from the skull surface in unrestrained, unanesthetized rats. Infrequent deviant tones presented randomly within a sequence of repetitive tones enhanced a long-latency positive component peaking at 240 msec. This rodent ERP was comparable to the human P3a component in latency and sensitivity to stimulus probability. The rodent may provide a useful model for investigation of the neural sources of the P3.
This study addressed the issue of multiple parallel auditory processing systems and their relationship to the skull-recorded auditory evoked potentials (AEPs) in the unanesthetized, unrestrained rat. In the preceding paper (Brain Res., 602 (1993) 240-250) it has been shown that auditory cortex activity does not contribute significantly to the vertex maximal AEPs recorded from the dorsal skull of the rat. In the present study, mapping of the AEP skull distribution revealed two sets of components: one set maximal at the dorsal skull vertex, and another set at the lateral skull), but not the early (P7-P11, N15) lateral skull components generated in auditory cortex. Bilateral auditory cortex ablation eliminated the lateral skull maximal AEP components, but not the dorsal skull maximal components. These findings support extensive parallel processing of auditory inputs (reflected by the dorsal AEPs) in the absence of primary auditory cortex. Ablation of primary auditory cortex did result in a modulation of the dorsal skull AEPs, indicative of an interaction between the geniculocortical system and the parallel system which generates the dorsal AEPs.
Abstract:
The objectives of this study were to characterize the auditory cortex response in the rat and to examine its contributions to the auditory evoked potentials (AEPs) recorded from the dorsal and lateral skull. This was accomplished by simultaneously recording AEPs from the cortical surface and from skull screw electrodes in anesthetized animals. The initial positive-negative response (P17-N32) was largely restricted to the cortical region corresponding to area 41. More detailed examination of the AEP mapping revealed multiple subcomponents (P9, P14, P17, P19) underlying the initial positivity, with differing topographies. Stimulus-response properties further dissociated the multiple positive subcomponents. Reversible local neurochemical suppression confirmed the auditory cortical origin of these AEPs. The auditory cortex-generated AEPs were refractory to barbiturate anesthesia which eliminated all dorsal skull AEPs, indicating that primary auditory cortical AEPs do not make a significant contribution to the dorsal skull-recorded ('vertex') AEPs. The findings raise issues regarding multiple parallel auditory processing systems and their associated AEPs.
Arthur P. Shimamura
Felicia B. Gershberg
Paul J. Jurica
Jennifer A. Mangels
Robert T. Knight
Date: 1992
PubMed: 1436439
Patients with frontal lobe lesions and control subjects were administered tests of word-stem completion priming. In this implicit memory test, subjects are first presented words (e.g. MOTEL, PARADE) in an incidental learning paradigm. Following word presentation, subjects are shown word stems (e.g. MOT, PAR) and asked to produce the first word that comes to mind. Patients with frontal lobe lesions exhibited normal levels of word-stem completion. These findings indicate that implicit memory can operate normally despite damage to the prefrontal cortex. The present results substantiate previous neuropsychological and positron emission tomography findings which indicate that word priming depends critically on posterior cortical areas.
Jaswinder Singh
Robert T. Knight
Nicholas Rosenlicht
Joan M. Kotun
Dennis J. Beckley
David L. Woods
Date: 1992
PubMed: 1358184
We assessed scalp-recorded movement related potentials (MRPs) generated prior to voluntary movements in chronic, medicated schizophrenics (n = 9) and age matched normal controls (n = 9). MRPs were recorded in a self-paced button press task in which subjects pressed a button with either their right, left or both thumbs (experimental condition I, II and III respectively). Controls generated a slowly rising readiness potential (RP) at about 1000 ms, a negative shift (NS') at about 450 ms and a motor potential (MP) at about 100 ms prior to movement. The initial MRP components (RP and NS') were reduced in schizophrenics indicating an impairment of the voluntary preparatory process in schizophrenia. Results of the present study indicate a similarity of MRP findings in schizophrenics and reported MRPs (Singh and Knight, 1990) in patients with unilateral lesions of the dorsolateral prefrontal cortex. These findings provide further support for frontal lobe dysfunction in schizophrenia.
Robert T. Wertz
Nina F. Dronkers
Ellen Bernstein-Ellis
Lisa K. Sterling
Yvonne Shubitowski
Roberta Elman
Gregory K Shenaut
Robert T. Knight
Jon L. Deal
Date: 1992
Telephonic and television technology was employed in a simulation study to determine its potential for providing appraisal and diagnosis of patients who suffer neurogenic communication disorders and reside in remote settings. Traditional, face-to-face appraisal and diagnosis was compared with appraisal and diagnosis by closed circuit television and computer-controlled video laserdisc over the telephone. Significant agreement in diagnosis among the three appraisal conditions and essentially the same performance on appraisal measures in all conditions suggests either closed circuit television or computer-controlled video laserdisc over the telephone could be substituted for traditional, face-to-face appraisal and diagnosis to reach patients who reside where traditional services do not exist.