Electrophysiological correlates of semantic features

Analyses of averaged auditory evoked responses to a list of 10 positive and 10 negative words led to the identification of a restricted region in the brain response which reliably discriminated between words differing in the semantic features positive and negative. These data support the view that word meanings are composed of more basic components or features and are not stored simply as dictionary items in the brain.     

Neuroelectrical correlates of hemisphere and handedness factors in a cognitive task

Principal-components analysis was performed on a set of averaged evoked potentials in order to extract components of cerebral activity functionally related to hemisphere, handedness, processing task, and stimulus feature variables. Eight such components were isolated. Degree of dextrality, hemispheric differences, and cognitive operations in processing distinct stimulus characteristics were identified as reflected in functionally distinct components of brain activity.     

Cortical involvement in the semantic processing of coarticulated speech cues

Auditory evoked responses (AER) were recorded from scalp locations over the left and right temporal regions in response to CVC words and nonsense syllables. Various components of the AER were found to vary systematically with changes in stimulus meaning. One such component reflected subcortical involvement in semantic processing. Other components reflected changes in voicing and place of articulation as well as hemisphere differences.     

Categorical perception for voicing contrasts in normal and lead-treated rhesus monkeys: electrophysiological indices

Categorical perception of voicing contrasts was evaluated in rhesus monkeys. The monkeys had been chronically exposed to subclinical levels of lead either from conception to birth, or for approximately 6 months postnatally beginning at birth, or were never exposed to lead. Auditory evoked responses were recorded at 1 year of age from scalp electrodes placed over the left and right hemispheres during stimulus presentation. A late component of the brain responses recorded from the right temporal region of all monkeys discriminated between stimuli in a categorical manner. This pattern of responses was noted to be similar to that previously reported for humans. Categorical discriminations were also noted earlier in the waveforms for control monkeys and for monkeys exposed to lead prenatally, although this discrimination pattern shifted to the left hemisphere of the latter group. No such effects were noted for monkeys exposed to lead postnatally. These results suggest that the neurocortical mechanisms associated with categorical perception for voicing information may be similar across human and nonhuman primates. However, early exposure to lead appears to alter these processes.     

Right-hemisphere responses from preschool children to temporal cues to speech and nonspeech materials: electrophysiological correlates

Auditory-evoked responses (AERs) were recorded from scalp electrodes placed over the left and right temporal hemisphere regions of 12 preschool children while they listened to a series of velar stop consonants which varied in voice onset time (VOT) and to two-formant tone stimuli with temporal lags comparable to the speech materials. A late occurring negative peak (N400) in the right hemisphere AERs discriminated between both the speech and nonspeech materials in a categorical-like manner. Sex-related hemisphere differences were also noted in response to the two different stimulus types. These results replicate earlier work with speech materials and suggest that temporal delays for both speech and nonspeech auditory materials are processed in the right hemisphere.