Online Theta Frequency Transcranial Alternating Current Stimulation for Cognitive Remediation in Schizophrenia: A Case Report and Review of Literature.

Transcranial alternating current stimulation (tACS), a noninvasive brain stimulation technique that uses low-intensity alternating current, has been postulated to be a potential therapeutic option in treating the cognitive deficits in schizophrenia. Transcranial alternating current stimulation synchronizes the neural oscillations to the applied stimulation frequency in the stimulated cortical regions. In this report, we have reviewed the literature pertinent to the clinical application of tACS in psychiatric disorders; in addition, we have described the clinical use of online theta tACS in a schizophrenia patient with cognitive deficits. Online theta tACS led to improvement in working memory, attention, processing speed, and emotional processing. The beneficial effect of tACS persisted during reassessment of the patient after 50 days. Transcranial alternating current stimulation, given its noninvasiveness, safety, and ease of administration, has the potential to ameliorate cognitive deficits in neuropsychiatric disorders like schizophrenia.

Auditory false perception in schizophrenia: Development and validation of auditory signal detection task.

Auditory hallucinations constitute an important symptom component in 70-80% of schizophrenia patients. These hallucinations are proposed to occur due to an imbalance between perceptual expectation and external input, resulting in attachment of meaning to abstract noises; signal detection theory has been proposed to explain these phenomena. In this study, we describe the development of an auditory signal detection task using a carefully chosen set of English words that could be tested successfully in schizophrenia patients coming from varying linguistic, cultural and social backgrounds. Schizophrenia patients with significant auditory hallucinations (N=15) and healthy controls (N=15) performed the auditory signal detection task wherein they were instructed to differentiate between a 5-s burst of plain white noise and voiced-noise. The analysis showed that false alarms (p=0.02), discriminability index (p=0.001) and decision bias (p=0.004) were significantly different between the two groups. There was a significant negative correlation between false alarm rate and decision bias. These findings extend further support for impaired perceptual expectation system in schizophrenia patients.