Reduced temporal activation during a verbal fluency test in clinical high risk of psychosis: a functional near-infrared spectroscopy-based study

Abstract

Background: Clinical high risk (CHR) of psychosis is a state in which positive symptoms cause the subjects distress but do not approach a severity level that fulfils the criteria for a psychotic episode. CHR exhibits cognitive deficits; however, the underlying neurobiological mechanisms remain unclear. This study aimed to investigate whether brain activation measured by the levels of oxygenated hemoglobin (oxy-Hb) in CHR subjects could be correlated with cognitive deficits.

Methods: Fifty-eight CHR individuals who fulfilled the criteria for attenuated positive syndrome as specified in the Structured Interview for Prodromal Syndrome (SIPS) and the Scale of Prodromal Syndrome (SOPS) and 58 age- and sex-matched healthy participants were included in the study. All subjects completed the Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) Consensus Cognitive Battery (MCCB) that includes tests measuring attention, verbal memory, verbal fluency, executive function, and general intelligence. Functional near-infrared spectroscopy (fNIRS) was used to measure the level of oxy-Hb in the dorsolateral prefrontal and frontotemporal cortices.

Results: We observed significantly decreased oxy-Hb levels in channel 32 (located in the right superior temporal gyrus, rSTG)) within the CHR individuals compared with that in the healthy controls (HCs) (t=-3.44, Bonferroni-corrected p=0.002), indicating lower brain activity. A significant positive correlation was observed between task-related β values and working memory in the CHR group (r=0.35, p=0.008).

Conclusions: The brain activation of rSTG is abnormal among subjects at clinicial high risk for psychosis. This abnormality is probably associated with the neural mechanisms of deficits in the working memory during the early stage of psychosis.

Keywords: cognition disorders; psychiatry; schizophrenia.

Figure 1

Flowchart of enrolment of the subjects. CHR, clinical high risk of psychosis; fNIRS, functional near-infrared spectroscopy; HC, healthy control; MCCB, Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) Consensus Cognitive Battery; NIRS, near-infrared spectroscopy.

Figure 2

(A) The verbal fluency test (VFT). It consists of a 30 s pretask resting-state period and three 20 s word-generating tasks, followed by a 70 s post-task resting-state period. (B) 3*11 optode montage. Red circles represent light sources (emitter), blue circles indicate light detectors, and numbers 1–52 indicate the location of each optode pair (channel). When we positioned the patch according to the International 10–20 system, detector 13 was located at Fz, and channels 49 and 46 were placed in Fp1 and Fp2, respectively. (C) The optode was placed on the bilateral frontal and temporal cortex. L, left; R, right.

Figure 3

Task-related β value of channel 32 in the CHR and HC group. CHR, clinical high risk; HC, healthy control.

Figure 4

Cortical activation map of oxy-Hb level during the VFT in different groups. (A) Compared with the HC group, the CHR group showed significantly decreased activation in Ch32; (B) Ch32 was located in the right superior temporal gyrus. Ch, channel; CHR, clinical high risk; HC, healthy control; oxy-Hb, oxy-haemoglobin; VFT, verbal fluency test.

Figure 5

Correlation analysis between task-related β values of channel 32 and cognition (working memory and verbal learning). The results showed that the β value had a significant positive correlation with working memory and showed a marginally significant level with the score of verbal learning in the CHR group, while there was no significant correlation found in the HC group. CHR, clinical high risk; HC, healthy control.