Tardive dyskinesia and associated cognitive disorders: a convergent neuropsychological and neurophysiological approach

The association between alterations in motor and cognitive dimensions of schizophrenia-spectrum disorders: A systematic review

Motor and cognitive alterations in schizophrenia-spectrum disorders (SSD) share common neural underpinnings, highlighting the necessity for a thorough exploration of the connections between these areas. This relationship is crucial, as it holds potential significance in unraveling the underlying mechanisms of SSD pathophysiology, ultimately leading to advancements in clinical staging and treatment strategies. The purpose of this review was to characterize the relationship between different hyper and hypokinetic domains of motor alterations and cognition in SSD. We systematically searched the literature (PROSPERO protocol CRD42019145964) and selected 66 original scientific contributions for review, published between 1987 and 2022. A narrative synthesis of the results was conducted. Hyper and hypokinetic motor alterations showed weak to moderate negative correlations with cognitive function across different SSD stages, including before antipsychotic treatment. The literature to date shows a diverse set of methodologies and composite cognitive scores hampering a strong conclusion about which specific cognitive domains were more linked to each group of motor alterations. However, executive functions seemed the domain more consistently associated with parkinsonism with the results regarding dyskinesia being less clear. Akathisia and catatonia were scarcely discussed in the reviewed literature. The present review reinforces the intimate relationship between specific motor alterations and cognition. Identified gaps in the literature challenge the formulation of definitive conclusions. Nevertheless, a discussion of putative underlying mechanisms is included, prompting guidance for future research endeavors.

Tardive dyskinesia: motor system impairments, cognition and everyday functioning

The recent approval of treatments for tardive dyskinesia (TD) has rekindled interest in this chronic and previously recalcitrant condition. A large proportion of patients with chronic mental illness suffer from various degrees of TD. Even the newer antipsychotics constitute a liability for TD, and their liberal prescription might lead to emergence of new TD in patient populations previously less exposed to antipsychotics, such as those with depression, bipolar disorder, autism, or even attention deficit hyperactivity disorder. The association of TD with activity limitations remains poorly understood. We review potential new avenues of assessing the functional sequelae of TD, such as the performance of instrumental activities of daily living, residential status, and employment outcomes. We identify several mediating aspects, including physical performance measures and cognition, that may represent links between TD and everyday performance, as well as potential treatment targets.

Comparison of the Halstead-Reitan and Infrared Light Beam Finger Tappers

Computer mediated motor tests can provide highly reliable means for evaluating gross and subtle aspects of psychomotor speed and rhythmicity. A computer mediated test of finger and foot tapping, making use of infrared light beam technology, was recently developed, but little is known regarding its psychometric properties. The purpose of this study was to compare performance of healthy right-handed respondents on the new Light Beam Finger & Foot Tapping Device to a traditional finger tapping test used in the Halstead-Reitan Neuropsychological Battery. Performance on the Halstead-Reitan Finger Tapping Test and on the Light Beam Finger Tapping Test was compared in 16 men and 17 women. The light beam test showed similar psychometric properties to those of the Halstead-Reitan Finger Tapping Test, and scores were moderately correlated between the two tests. Respondents had faster scores on the light beam test; on both tests men were faster than women, and all respondents tapped faster with their dominant hand. Tapping was faster on the Light Beam Finger Tapping Test, possibly because it does not require application of pressure to a mechanical key and a smaller movement registers a tap. In addition to measures of right- and left-hand tapping speed, the light beam test assesses synchronous and alternating tapping and foot tapping. Scores between these subtests showed moderate to high correlations.

An auditory processing abnormality specific to liability for schizophrenia

Abnormal brain activity during the processing of simple sounds is evident in individuals with increased genetic liability for schizophrenia; however, the diagnostic specificity of these abnormalities has yet to be fully examined. Because recent evidence suggests that schizophrenia and bipolar disorder may share aspects of genetic etiology the present study was conducted to determine whether individuals with heightened genetic liability for each disorder manifested distinct neural abnormalities during auditory processing. Utilizing a dichotic listening paradigm, we assessed target tone discrimination and electrophysiological responses in schizophrenia patients, first-degree biological relatives of schizophrenia patients, bipolar disorder patients, first-degree biological relatives of bipolar patients and nonpsychiatric control participants. Schizophrenia patients and relatives of schizophrenia patients demonstrated reductions in an early neural response (i.e. N1) suggestive of deficient sensory registration of auditory stimuli. Bipolar patients and relatives of bipolar patients demonstrated no such abnormality. Both schizophrenia and bipolar patients failed to significantly augment N1 amplitude with attention. Schizophrenia patients also failed to show sensitivity of longer-latency neural processes (N2) to stimulus frequency suggesting a disorder specific deficit in stimulus classification. Only schizophrenia patients exhibited reduced target tone discrimination accuracy. Reduced N1 responses reflective of early auditory processing abnormalities are suggestive of a marker of genetic liability for schizophrenia and may serve as an endophenotype for the disorder.

Tardive dyskinesia and antipsychotics: a 5-year longitudinal study of frequency, correlates and course

The present study comprised a naturalistic, multicentre, 5-year study of course and correlates of tardive dyskinesia (TD). One hundred and sixty-six patients treated with risperidone were included during 1995/96 and followed once a year for 5 years. Mean age at inclusion was 38 years, and mean illness duration was 12 years. Tardive dyskinesia was assessed by the Abnormal Involuntary Movement Scale, and each patient's cognitive function was tested with a comprehensive computerised test battery. At study entry, 14% had TD according to a criterion index. Fifty percent were aware of it, but few reported distress. Age and sex did not correlate with TD, but schizophrenia and bipolar diagnoses did. The presence and intensity of TD correlated with all Positive and Negative Syndrome Scale for Schizophrenia symptom dimensions except the affective factor, but not with type of medication or chlorpromazine-equivalent levels. Tardive dyskinesia patients were cognitively impaired in tests reflecting mental speed, but not in other cognitive modalities. Over the 453 patient years of exposure, five patients developed TD and 14 became free of it. Our findings support the view that TD: (i) is a dynamic phenomenon; (ii) is only partly drug-induced; (iii) has a mild course during treatment with modern neuroleptics; and (iv) appears to have some correlation with mental slowness.

N2 and P3 components of event-related potential in first-episode schizophrenic patients: scalp topography, medication, and latency effects

Auditory N2 and P3 components of event-related potentials were assessed in first-episode schizophrenic and normal control subjects (n=12/group). P3 amplitude was decreased in the patients most prominently over the frontal areas in contrast to a widespread P3 amplitude decrease reported in chronic schizophrenia. Moreover, frontal attenuation of P3 amplitude was greater in the non-medicated compared with medicated patients, a finding that suggests frontal areas are primarily affected at the onset of the first schizophrenic episode. Prolongation of N2 and P3 latencies was also observed in the patients, which indicates that stimulus classification and memory updating processes were slowed even in early stages of schizophrenia. These findings indicate that first-episode schizophrenic patients produce N2 and P3 abnormalities that are distinct from those in chronic patients, and that psychotropic medication can attenuate event-related potential effects in specific ways.

Auditory evoked potentials, clinical vs. research applications

Evidence of abnormal auditory evoked potentials (EPs) in patients suffering from schizophrenia has been accumulating. In spite of the magnitude of the EPs in schizophrenia literature, EPs have not been found to be clinically useful thus far. In this study we attempted to replicate the findings in a large sample of schizophrenia patients, and describe how auditory EPs may be used as supplemental tests in the differential diagnostic process. Five subject groups were formed; paranoid (PAR) and disorganized/undifferentiated (disorg/undiff) schizophrenics, schizoaffective (SA), bipolar, and a normal control group. All patients were stable on medications. Subjects underwent one EP recording session. Classification and regression trees (CART) based on EP amplitudes were used to classify subjects into subgroups. The optimal Bayes classification rule that minimizes the expected misclassification cost was then constructed for various misclassification cost functions. In a standard 'Odd Ball' paradigm the N100 amplitudes were significantly decreased in the disorg/undiff group than in the bipolar or normal subjects. The P200 amplitude was smaller in the PAR, disorg/undiff and the SA groups than in the normal controls. Both the disorg/undiff and the PAR groups had significantly lower P300 amplitudes than the normal controls. Classification rules used to classify subjects into normal or ill were sensitive to the relative cost of misclassifying a subject, as well as the prior clinical probability that this subject was ill. Our data largely agree with the existing literature showing abnormally decreased N100, P200, and P300 amplitudes in schizophrenic patients, particularly the disorg/undiff patients. We conclude that whether EP measures are clinically useful depends on the clinical situation. In particular, the prior probability of the diagnosis in question being present and the cost of misclassifying the patient are critical.