Dichotic shadowing and selective attention to word meanings in schizophrenia

Dichotic listening impairments in early onset schizophrenia are associated with reduced left temporal lobe volume

Dichotic listening (DL) impairments, in particular the loss or reduction of right ear advantage (REA) in people with schizophrenia have been variously interpreted as both a state and trait marker for schizophrenia. To date, there has been no comprehensive investigation of dichotic language impairments in relation to the structural integrity of the temporal cortex--the likely neural substrate for such impairments. In this study of 39 early onset patients and matched controls we used a dichotic listening procedure and examined the findings in relation to MRI measurements of gross and regional cerebral volumes. No overall group difference in ear advantage was found between patients and controls but patients who showed absence of REA also demonstrated an accompanying reduction of left temporal lobe volume compared with patients who showed normal ear advantage and controls. The findings suggest that impaired DL performance is a correlate of structural change in the temporal lobe and that this is apparent in early onset cases.

Normal sustained effects of selective attention are absent in schizophrenic patients withdrawn from medication

Sustained attentional deficits have been widely reported in groups of medicated schizophrenic patients, but less is known about sequential attentional processes in patients withdrawn from medication. The attentional performance of 12 medication-withdrawn schizophrenic outpatients was compared with that of 16 matched normal volunteers on a Stroop negative priming task. This task allowed examination of both within-trial and between-trial attentional effects. Compared with the volunteers, the medication-withdrawn schizophrenic patients showed normal within-trial attentional effects as measured by standard Stroop interference and facilitation. Across trials, however, the schizophrenics exhibited reduced negative priming compared with the volunteers and in some cases a complete reversal of sustained inhibitory processes. The findings suggest that a normal inhibitory tag occurred during initial selection in the patient group, but it did not influence a subsequent act of selection as was the case for the normal volunteers. Either inhibition decayed at an abnormally fast rate in the patient group or a separate facilatory tag dominated. In either case, priming effects linked to attentional selection were clearly abnormal in the medication-withdrawn patient group.

Distraction resulting from disease related words in alcohol-dependent inpatients: a controlled dichotic listening study

To test whether alcoholics develop an information processing bias towards disease-related stimuli, 30 alcoholic inpatients and 30 controls were administered a dichotic listening task. Three different stimulus types were presented to the right (ignored) channel: neutral words, rare neutral words and alcohol-related words. The hypothesized information processing bias should cause patients to make disproportionally more shadowing errors in the third condition. An ANOVA revealed a significant condition effect (P < 0.001), a tendency towards a group effect (P = 0.09) and a significant interaction (P < 0.01) in the expected direction. There was a marked increase of errors in alcoholics when disease-related stimuli were presented compared to the neutral conditions and to the controls.

Attentional functions in listening and schizophrenia. A selective review

Maintaining the focus on one sound object or shifting it to another are considered to be two important attentional functions in selective listening, which may serve to differentiate attentional deficits in schizophrenics with respect to their psychopathology. To avoid confounding attentional control with effects of cerebral organization (laterality) as in dichotic listening, it is suggested that spatial hearing is taken into account when testing these attentional operations.

An analysis of the skin conductance orienting response in samples of American, British, and German schizophrenics

The existing literature dealing with the phasic orienting response (OR) in schizophrenia, examining, for the most part, the skin conductance component (SCOR), reports conflicting results with divergent implications for the nature of the attentional dysfunction in these patients. The present authors have contributed to that literature and to its divergencies. The present report addresses this issue by applying a common set of response definitions and uniform statistical-analytic procedures to the previously gathered electrodermal data obtained independently in each author's laboratory. A total of 14 studies is involved, drawn from six laboratories in the U.S.A., the U.K., and West Germany. Collectively, these studies examine chronic and acute schizophrenics, males and females, those receiving neuroleptic drugs and those not receiving them, recording SCOR from either (or both) hands using a variety of instruments and somewhat differing instructions and conditions, to both auditory and visual stimuli of different intensities and rise-time properties. The authors' purpose is two-fold. First, to determine whether some 'universal' dysfunction can be demonstrated across laboratories, conditions, and samples. Given the heterogeneous origins of these data such a finding would offer fairly strong evidence of 'real' dysfunction in schizophrenia. Second, where disagreement exists, to describe the scope and nature of the disagreement, and to articulate more clearly the findings on each side of a disputed area. One such 'universal' dysfunction emerged. Consistently, schizophrenics displayed an abnormally high incidence of nonresponsiveness, involving nearly 50% of the schizophrenic sample on average. The next most common finding is that many of the schizophrenics who display an SCOR often habituate faster than do nonschizophrenic responders. This was seen in a majority of the studies and laboratories, but conflicting evidence was presented by a minority. Evidence for a dysfunction simultaneously involving SCOR hypo- and hyper-responsiveness within schizophrenia was obtained, but in a minority of studies. The possible effects of neuroleptic drugs, stimulus intensity and rise-time factors, and differential significance evaluation on these findings was discussed. The possibility that schizophrenic dysfunction involves the input-facilitating OR but not input-attenuating 'protective' responses is examined. The correlates of hyporesponsiveness in schizophrenia, including physiological response patterns, clinical symptom patterns, and specific input deficiencies, is also examined. Several areas are noted where systematic research has only begun, and further study is particularly needed.

Electrodermal activity and vulnerability to schizophrenia: a review

Because electrodermal variables show consistency over time and situations, and evidence of genetic loading, it is of interest to examine such measures in adult schizophrenics and in children at risk for the disorder. Samples of adult schizophrenics are heterogeneous with regard to electrodermal activity. One group, the nonresponders, fails completely to respond to simple moderate intensity nonsignal stimuli. The other, the responders, does not differ from normals in frequency of response to nonsignal stimuli, but tends to show elevated tonic levels, and bilaterally asymmetrical and rapidly recovering responses. These two groups differ in other physiological and psychological measures, and in clinical picture. The responder pattern is predictive of poor outcome of acute schizophrenic episodes. A similar hyperactive pattern was found to differentiate children genetically at high or low risk for schizophrenia, and to predict psychiatric breakdown in the former group in Mednick and Schulsinger's original high risk study. The relationship to risk has been less evident in later studies, but similar, albeit weaker, tendencies have been reported. It is concluded that the nonresponding pattern may be secondary to a clinical picture of withdrawal and confusion, whereas the responder pattern may index vulnerability to schizophrenic episodes. On the psychological level, it is argued that this relationship is best conceptualized in attentional terms couched in information-processing language.