Central auditory processing : III. The “cocktail party” effect and anterior temporal lobectomy

The capacity to selectively attend to only one of multiple, spatially separated, simultaneous sound sources—the “cocktail party” effect—was evaluated in normal subjects and in those with anterior temporal lobectomy using common environmental sounds. A significant deficit in this capacity was observed for those stimuli located on the side of space contralateral to the lobectomy, a finding consistent with the hypothesis that within each anterior temporal lobe is a mechanism that is normally capable of enhancing the perceptual salience of one acoustic stimulus on the opposite side of space, when other sound sources are present on that side. Damage to this mechanism also appears to be associated with a deficit of spatial localization for sounds contralateral to the lesion.     

Central auditory processing : II. Effects of anterior temporal lobectomy

Ear dominance for the pitch of dichotically presented tonal stimuli was measured in nine patients before and after a unilateral anterior temporal lobectomy. Four subjects had a left and five had a right lobectomy. Every patient exhibited a change of ear dominance consistent with the hypothesis that a unilateral lobectomy decreases the perceptual salience of the tone presented to the ear contralateral to the lesion. Depending on the direction and magnitude of the subject's preoperative ear dominance and the side of the lobectomy, the postoperative results either increased or decreased the strength of ear dominance in a predictable fashion. The results support the idea that within each temporal lobe lie physiological mechanisms which can enhance the perceptual salience of the acoustic signal emitted by one sound source when other, concurrent, spatially separated sound sources are present. It is also argued that the same mechanism operates on speech, melodic, and tonal signals.     

Central auditory processing. VI. Detecting ear dominance by evoked potentials

An electrophysiological method is described for measuring the direction and strength of a subject's ear dominance for pitch using the P3 component of event-related potentials. Results of these experiments reveal that the P3 can be used effectively for these measures in man.     

Central auditory processing: I. Ear dominance—A perceptual or an attentional asymmetry?

The phenomenon of ear dominance for pitch described by Efron and Yund has been attributed by them to an asymmetry of sensory origin in the binaural integration of dichotic tone pairs. An explanation of this phenomenon in terms of an attentional bias is rejected on the basis of two experiments where the possibility of such bias was excluded. These and other experiments indicate that a simple explanation of this ear dominance in terms of a hemispheric specialization in the processing of tonal stimuli also must be rejected.     

Spectral versus temporal features in dichotic listening

Ear advantage for the processing of dichotic speech sounds can be separated into two components. One of these components is an ear advantage for those phonetic features that are based on spectral acoustic cues. This ear advantage follows the direction of a given individual's ear dominance for the processing of spectral information in dichotic sounds, whether speech or nonspeech. The other factor represents a right-ear advantage for the processing of temporal information in dichotic sounds, whether speech or nonspeech. The present experiments were successful in dissociating these two factors. Since the results clearly show that ear advantage for speech is influenced by ear dominance for spectral information, a full understanding of the asymmetry in the perceptual salience of speech sounds in any individual will not be possible without knowing his ear dominance.     

Processes of verbal memory failure in Alzheimer-type dementia

Multiple aspects of verbal learning and memory performance in mild as compared to moderate Alzheimer-type dementia (ATD) were studied with the Buschke selective reminding paradigm. Results show that (1) both groups of ATD subjects depend less on long-term memory (LTM) and more on short-term memory (STM) relative to elderly control subjects, (2) mild ATD subjects show less LTM encoding than moderate ATD subjects, (3) moderate ATD subjects retrieve a smaller portion of the items presumed to be encoded into LTM than do mild ATD subjects, and (4) high-imagery words increase LTM encoding and retrieval as compared to low-imagery words for moderate ATD subjects only. These results are explained by the inability of ATD subjects to attend to more than one component of the list-learning task, in conjunction with differences in the deployment of attention between mild and moderate ATD subjects.     

The perception of dichotic chords by hemispherectomized subjects

Hemispherectomized subjects display a strong ear dominance in their perception of dichotically presented two-tone chords. The frequency of the tone presented to the ear contralateral to the remaining hemisphere dominated the pitch mixture of the chord. The described effect does not vary with the age at which the hemispherectomy was performed. These results are consistent with the hypothesis, developed to account for findings in normal subjects, that the pitch mixture of a dichotic chord is determined by a subcortical pitch processor. The effects observed in hemispherectomized subjects may result from an interruption of an efferent pathway from the cortex to the subcortical pitch processor or from an asymmetrical degeneration of the processor which may be located in the thalamus (medial geniculate).     

Development of differences in response latencies to right and left visual fields

Robust lateralization developed in right-handed adults who were asked to judge letter pairs as "same" or "different" during 4608 trials. By the end of the first two blocks (768 trials) "same" responses were favored when presented in the RVF (transmitted directly to the left hemisphere) and "different" responses were favored when presented in the LVF (transmitted direction to the right hemisphere). This gradually reversed over sessions with "same" responses becoming faster for letters presented in the LVF, and "different" responses becoming faster for stimuli presented in the RVF. The laterality acquired under these conditions was cumulative and reproducible, appeared in all 16 subjects, and was preserved between sessions a week apart. The data suggest that laterality is a flexible and reversible characteristic of the human brain even when stimulus and task remain constant.     

Paralinguistic aspects of auditory comprehension in aphasia.

Eight severe aphasics were given sentences with either emotional or neutral content, presented once directly by the examiner and once via a tape recorder. Sentences with emotional content produced a greater number of responses than their neutral counterparts. Sentences spoken by the examiner also produced a significantly greater number of responses than the same items originating from a tape recorder. These results confirm the view that elements not related to the linguistic aspects of a message (and therefore referred to as paralinguistic) play a significant role in auditory comprehension.     

Intelligence and the processing of stimulus structure

It has been demonstrated in a number of experiments that the difficulty level of several performance type intelligence test tasks is determined directly by stimulus and task variables that vary the information to be processed. The variables are quantifiable. The implications of these findings for intelligence and the problems of an experimental approach to the measurement of intelligence are discussed.     

Workers' central life interests and personality characteristics

Industrial workers who perceive work as their central life interest (CLI) also describe themselves as having a higher level of decisiveness, initiative, and supervisory ability than workers with other CLI orientations. Workers with CLI orientations in nonwork institutions have the lowest scores on decisiveness, need for occupational achievement, and initiative, and the highest need for job security, of the groups studied. Workers with no anchored CLI had the highest need for self-actualization and need for occupational achievement, of all groups. These personality characteristics are seen as consistent with the CLI orientations of individual workers, suggesting that the personality does “fit” some institutional setting, but not necessarily all those in which the individual functions.     

Young children's processing of television: Modality differences in the retention of temporal relations

Two experiments were conducted to examine modality differences in pre-schoolers' ability to recognize or recall temporally related events. Results of both experiments demonstrated that temporally related events were remembered more frequently when they were conveyed visually rather than aurally. This modality effect was found both when the semantic content of the auditory and visual sequences was either the same or different, and for shows designed for educational and purely entertainment purposes. The data suggest that children show relatively impoverished integration of the temporal parameters of auditory information, which may contribute to their misunderstandings about the plot of a televison show.     

Motivation and learning: Neurophysiological mechanisms in a “model” system

The neurophysiological mechanisms underlying behavioral motivation and associative learning are described in an invertebrate “model” system, the carnivorous marine mollusc Pleurobranchaea. Feeding motivation can be controlled via nutritional history and is represented centrally in the feeding motor network as a change in the balance of synaptic excitation and inhibition at the level of interneurons that initiate feeding behavior, i.e., feeding “command” interneurons. Associative learning, induced by avoidance conditioning of feeding behavior, manifests identically at the level of the command interneurons, but is distinguished from non-associative motivational changes by processes that occur in identified neurons and pathways presynaptic to the command interneurons. Motivation and learning are therefore linked mechanistically by convergent neurophysiological mechanisms at the level of central neurons that initiate behavior.     

Verbal and nonverbal recognition memory in aphasic and nonaphasic stroke patients

The ability to retain lists of verbal and nonverbalizable items across recurrent recognition tasks was tested in three groups: (1) stroke patients with a left-brain lesion and aphasia, (2) stroke patients with a right-brain lesion and left hemiplegia, and (3) nonneurologically impaired outpatients. As determined with signal detection measures, aphasics were deficient in discriminating words that were to be remembered from those that were not; their recognition of nonverbal visual (geometric art) or auditory (bird calls) patterns, however, was unimpaired. Left hemiplegics showed the opposite pattern. After a long-term interval (<10 min), correct recognition of words was diminished in all groups whereas recognition of visual patterns increased. Both groups of stroke patients adopted material-specific decision criteria which in part accounted for the dissociation of verbal and nonverbal recognition memory by laterality of lesion. Item analysis indicated that aphasics' verbal memory difficulties were affected by acoustic-semantic confusion of list words.     

A note on temporal relations between language and gestures

The initiation of the spontaneous gestures of Wernicke's aphasics was analyzed in relation to shifts in semantic content between the syntactic boundaries of main clauses and embedded clauses. Gestures proved more likely to arise at the initial boundaries of embedded clauses when these were semantically discontinuous with the main clause than when these were semantically related to the main clause. Spontaneous gestures may signal underlying shifts in semantic intention, thereby reflecting the difficulties encountered by Wernicke's aphasics in maintaining a coherent stream of thought across syntactic boundaries.