Selective attention, contingent negative variation and the evoked potential

Contingent negative variation (CNV), N1-P2 amplitude of the evoked potential (EP), and positivity at 300, 400 and 500 msec latency (P300, P400 and P500) were measured in relation to task relevant (R) or irrelevant (I) tones presented alternately or unpredictably at 1 sec intervals. High concordance of P300, 400 and 500 indicated a slow, relatively unpeaked wave thought to be the CNV resolution. Both N1-P2 and P300 appeared small only when stimuli were both irrelevant and predictably so. With predictable presentation correlations were observed between CNV, N1-P2 and P300 in terms of both absolute level and, particularly, relevant/irrelevant difference. Holding CNV constant statistically, and to a lesser extent P300, reduced these correlations. It is suggested that CNV resolution in the post-stimulus trace reflects selective attention paid to the stimulus, and may be responsible, through summation, for claims that N1-P2, and sometimes P300, does so.     

Selective attention and Pavlovian conditioning

The present results show that the common practice of using self-indexing conditioned stimuli (CSs) in research on Pavlovian conditioning is a major source of experimental bias. The typical stimulus used is either a light flash or a sound pulse in a light/sound-shielded chamber. Under these conditions the onset characteristics of the CS signal totally predominate over the durational characteristic, i.e. the pattern information. Thus a visual pattern presented as a CS in a dark chamber is confounded with a brightness change from darkness to light. In the first experiment, animals were conditioned with a brightness CS using a self-indexing signal paradigm. When tested for specificity of the conditioning, they showed complete transfer of learning to either a visual pattern or even an auditory CS. These findings indicated that the traditional conditioning paradigm is biased towards non-specific sensory learning. The second experiment showed that specific sensory conditioning is critically dependent on selective attention mechanisms. When the onset characteristics of the CS signal were de-emphasized by the use of equal energy background illumination in the intertribal interval (ITI) during conditioning, the animals were not able to feature extract either the onset or the durational component of the CS signal from the ITI background despite prolonged training. It was only by starting with conditioning that was initially anchored to the CS onset characteristics that a perceptual fade-in procedure would bias attention to feature extract the durational characteristics of the CS. Thus conditioning occurred only when the rabbit’s attention was directed to detection of the gratings display without any associated changes in visual albedo. Perhaps the most important finding of the present experiments is that the use of self-indexing CS signals in Pavlovian conditioning inevitably introduces non-specific sensory processing involving multiple sensory input pathways in the conditioning. This inherent uncertainty of the sensory input pathways presents a problem for clarifying the role of sensory pathways in the neural mechanisms of NM conditioning. In addition, the use of self-indexing CSs inevitably leads to an underestimation of the role of forebrain mechanisms in Pavlovian conditioning.     

Narcissistic depression in schizophrenia

In individual analytically oriented psychotherapy as a research method, observing a random sample of 34 schizophrenics with the symptoms of depressive syndrome, the author has found that depression in schizophrenia is determined by narcissistic injuries, by a collapse of narcissistic satisfactions through the loss of "ego" functions, completeness, competitiveness, and competence. The depressive model is most frequently encountered in florid schizophrenic psychosis, at the beginning of hospitalization, but depending on the intensity and depth of narcissistic traumas and losses, it can develop also in any phase of the therapeutic process and the course of illness. In the author's view, the depressive model in schizophrenia is not conditioned by the neuroleptic treatment. Its recognition is very important for the therapy of suicidal tendencies, and for their prevention in particular.     

Active and passive attention in schizophrenia: an ERP study of information processing in a linguistic task.

Attentional dysfunctions in schizophrenia were investigated using a sentence priming task. Schizophrenic patients and healthy control subjects were presented with sentences to which they were required to make a response based on either semantic or physical stimulus features. Schizophrenics' behavioural responses were slower than those of controls, particularly when attending to semantic relationships, but their performance was no less accurate. Both the P300 and the N400 components of the event-related potentials (ERPs) recorded to the sentence completions were attenuated in the schizophrenic sample. The results are interpreted in terms of a deficit in the active maintenance of semantic information in memory and the integration of new information with this representation.     

Sustained attention in young people at high risk for schizophrenia

BACKGROUND: Sustained attention has been found to be impaired in individuals suffering from schizophrenia and their close relatives. This has led to the hypothesis that impaired sustained attention is an indicator of vulnerability to schizophrenia. METHODS: The Edinburgh High Risk Study used the Continuous Performance Test-Identical Pairs version (CPT-IP) to assess sustained attention in 127 high risk participants, 30 controls and 15 first-episode schizophrenic patients. A second assessment was completed by 59 high risk and 18 control participants 18 months to 2 years after the first. RESULTS: No differences in attentional capacity were found between the high risk and control groups and there was no association between genetic liability to schizophrenia and poor performance on the CPT-IP. Additionally, no association between occurrence of psychotic symptoms in the high risk group and impaired attentional capacity was found. CONCLUSIONS: The results suggest that deficits in sustained attention are not indicative of a genetic vulnerability to schizophrenia, and are not associated with the occurrence of psychotic symptoms.     

Selective attention and active engagement in young children

During early development, significant changes occur in the neural regions that subserve attention and related skills. Although preschoolers typically have difficulty performing continuous performance tests, it is not clear if this is primarily due to an inability to selectively respond or an inability to maintain attention. A group of 52 children between 3.5 and 5.5 years of age performed 2 vigilance-type reaction time tasks. The tasks included short duration, continuously presented visual stimuli across several short blocks. Among the children under 4.5 years of age, 46% were unable to coordinate the necessary task demands, and those who could made significantly more omission errors than the older children. Active engagement was high during the reaction time tasks for all children. These results suggest that the skills necessary for vigilance tasks, particularly speeded response initiation and response selection, are still emerging during the preschool years but can be adequately measured after 4.5 years of age.     

Selective processing of threatening information: effects of attachment representation and anxiety disorder on attention and memory

To investigate the effect of the mental representation of attachment on information processing, 28 anxiety disorder outpatients, as diagnosed by the Anxiety Disorders Interview Schedule-Revised, were administered the Adult Attachment Interview and the State-Trait Anxiety Inventory. They also completed an emotional Stroop task with subliminal and supraliminal exposure conditions, a free recall memory task, and a recognition test. All tasks contained threatening, neutral, and positively valenced stimuli. A nonclinical comparison group of 56 participants completed the same measures. Results on the Stroop task showed color-naming interference for threatening words in the supraliminal condition only. Nonclinical participants with insecure attachment representations showed a global response inhibition to the Stroop task. Clinical participants with secure attachment representations showed the largest Stroop interference of the threatening words compared to the other groups. Results on the free recall task showed superior recall of all types of stimuli by participants with secure attachment representations. In the outpatient group, participants with secure attachment representations showed superior recall of threatening words on the free recall task, compared to insecure participants. Results on the recognition task showed no differences between attachment groups. We conclude that secure attachment representations are characterized by open communication about and processing of threatening information, leading to less defensive exclusion of negative material during the attentional stage of information processing and to better recall of threatening information in a later stage. Attachment insecurity, but not the type of insecurity, seems a decisive factor in attention and memory processes.     

Brain connectivity in positive and negative syndrome schizophrenia

If, as is widely believed, schizophrenia is characterized by abnormalities of brain functional connectivity, then it seems reasonable to expect that different subtypes of schizophrenia could be discriminated in the same way. However, evidence for differences in functional connectivity between the subtypes of schizophrenia is largely lacking and, where it exists, it could be accounted for by clinical differences between the patients (e.g. medication) or by the limitations of the measures used. In this study, we measured EEG functional connectivity in unmedicated male patients diagnosed with either positive or negative syndrome schizophrenia and compared them with age and sex matched healthy controls. Using new methodology (Medkour et al., 2009) based on partial coherence, brain connectivity plots were constructed for positive and negative syndrome patients and controls. Reliable differences in the pattern of functional connectivity were found with both syndromes showing not only an absence of some of the connections that were seen in controls but also the presence of connections that the controls did not show. Comparing connectivity graphs using the Hamming distance, the negative-syndrome patients were found to be more distant from the controls than were the positive syndrome patients. Bootstrap distributions of these distances were created which showed a significant difference in the mean distances that was consistent with the observation that negative-syndrome diagnosis is associated with a more severe form of schizophrenia. We conclude that schizophrenia is characterized by widespread changes in functional connectivity with negative syndrome patients showing a more extreme pattern of abnormality than positive syndrome patients.     

Differentiating attention deficit in adult ADHD and schizophrenia.

Most previous studies of attention deficit in ADHD and schizophrenia have used overall measures of inattention that may disguise differences in underlying mechanisms. The present study investigated types of inattentive errors and applied a process view of attention in analyses of Conners' Continuous Performance Test protocols from subjects with ADHD-combined (51), inattentive type (19) and schizophrenia (26). Subjects with ADHD-I had more omission errors and became more inattentive as a function of time on task. Subjects with ADHD-C made more errors of commissions as time passed. In contrast, the performance of the subjects with schizophrenia improved, indicating a training effect. There were no differences in overall attentiveness between the groups. Although all groups were impaired on an overall level, they displayed three distinct patterns of inattention. The ADHD-I group displayed a lethargic inattention characterized by high fatigue. The ADHD-C group showed a hyperactive-impulsive pattern, while the schizophrenia group showed an inability to initially focus attention.     

Selective attention impairments in Alzheimer's disease: evidence for dissociable components

Tasks emphasizing 3 different aspects of selective attention-inhibition, visuospatial selective attention, and decision making-were administered to subjects with mild Alzheimer's disease (AD) and to healthy elderly control (HEC) subjects to determine which components of selective attention were impaired in AD subjects and whether selective attention could be dissociated into different components. The tasks were administered with easy versus hard levels of difficulty to assess proportional slowing as the key variable across tasks. The results indicated that the inhibitory and visual search tasks showed greater proportional slowing in subjects with AD than in HEC subjects, and that the task involving inhibition was significantly more affected in subjects with AD. Furthermore, there were no significant intertask correlations, and the results cannot be explained simply in terms of generalized cognitive slowing. These results provide evidence that inhibition is the most strikingly affected aspect of selective attention that is observed to be impaired in early stages of AD.     

Syntactic complexity and negative symptoms in first onset schizophrenia

This paper compares the syntactic features of three groups of subjects: first onset schizophrenics with negative symptoms (n=17); with no negative symptoms (n=18); and nonpsychiatric controls (n=16). The speech of schizophrenic subjects contained more syntactically and semantically deviant sentences. The negative symptom group produced shorter sentences that contained lower levels of clausal embedding. Most of these differences were related to group differences in social class, attentional deficits in the schizophrenic group, or collinearity between sentence length and clausal complexity. Despite this, the difference in clausal complexity persisted after the effects of these confounding variables had been removed. This indicates that reduced syntactic complexity is an important feature of the speech of patients in whom negative symptoms are prominent. The significance of this finding is discussed in relation to recent theories of schizophrenia.     

Anticipation in schizophrenia and bipolar disorder controlling for an information bias

Anticipation was investigated in schizophrenia (SZ) and bipolar disorder (BP) while addressing several biases in 18 large families (154 subjects) from Eastern Québec densely affected by SZ, BP, or both over three generations. In particular, we controlled for an information bias using a measure of quality and quantity of clinical information (QOI) concerning the subjects' illness. Otherwise, spurious anticipation could have arisen because we found that QOI varied with the generations as well as with the severity of illness. Although anticipation was investigated separately for SZ and BP, both disorders were also included in one analysis that tested anticipation under the unitary hypothesis that the SZ and the BP spectrums represent a continuum of severity of the same disease. Age of onset (AOO) and five indices of severity were tested for anticipation. Two statistics were used: the difference in the mean AOO or severity between two successive generations, and the mean difference in parent-offspring pairs (POP). The study led to four main findings: 1) the choice of the statistics greatly influenced the results, POP yielding systematically greater biased estimates; 2) for SZ and BP, the evidence for anticipation with the five severity indices vanished after controlling for QOI; 3) as regards AOO a decrease of 8.6 years, p = 0.0001, and 5.3 years, p = 0.009 in AOO was found for SZ between Generations 1-2, and 2-3, respectively, despite controlling for QOI and addressing all biases; and 4) conversely for BP, anticipation with AOO may be due to censoring. Findings suggest that future anticipation studies should also control for QOI. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:61-68, 2000.     

Second-order facial information processing in schizophrenia

This study investigated the processing of second-order relational face information in schizophrenia. Twenty-eight schizophrenic patients and 28 controls were asked to say whether the space between the eyes was the same in 2 side-by-side faces. The 2 faces were derived from the same original face, but the spacing between the eyes was either the same or differed by various distances. The results showed that schizophrenic patients needed a space that was twice as great as controls to see a difference. The authors conclude that schizophrenic patients have a deficit in processing second-order relational face information.     

Methylenetetrahydrofolate reductase variant and schizophrenia/depression

Patients with methylenetetrahydrofolate reductase (MTHFR) deficiency often show psychiatric manifestations. Since a common variant of the MTHFR gene, T677(Ala), responsible for the thermolabile MTHFR with less than 50% specific MTHFR activity, has been reported, we examined whether the T677 allele is associated with psychiatric disorders in an unrelated Japanese population consisting of 297 schizophrenics, 32 patients with major depression, 40 patients with bipolar disorder, and 419 controls. The genotype homozygous for the T677 allele was significantly frequently observed in schizophrenics with an odds ratio of 1.9 (P = 0.0006), and in patients with major depression with an odds ratio of 2.8 (P = 0.005). Our data suggest associations of the MTHFR gene variant with schizophrenia and depression in the Japanese. Am. J. Med. Genet. 74:526–528, 1997. © 1997 Wiley-Liss, Inc.