Previous findings have shown that individuals with autism spectrum disorder (ASD) evince greater intra-individual variability (IIV) in their sensory-evoked fMRI responses compared to typical control participants. We explore the robustness of this finding with a new sample of high-functioning adults with autism. Participants were presented with visual, somatosensory and auditory stimuli in the scanner whilst they completed a one-back task. While ASD and control participants were statistically indistinguishable with respect to behavioral responses, the new ASD group exhibited greater IIV relative to controls. We also show that the IIV was equivalent across hemispheres and remained stable over the duration of the experiment. This suggests that greater cortical IIV may be a replicable characteristic of sensory systems in autism.

Mismatch negativity (MMN) to deviant stimuli is robustly smaller in individuals with chronic schizophrenia compared with healthy controls (Cohen’s d > 1.0 or more), leading to the possibility of MMN being used as a biomarker for schizophrenia. However, there is some debate in the literature as to whether MMN is reliably reduced in first-episode schizophrenia patients. For the biomarker to be used as a predictive marker for schizophrenia, it should be reduced in the majority of cases known to have the disease, particularly at disease onset. We conducted a meta-analysis on the fourteen studies that measured MMN to pitch or duration deviants in healthy controls and patients within 12 months of their first episode of schizophrenia. The overall effect size showed no MMN reduction in first-episode patients to pitch-deviants (Cohen’s d < 0.04), and a small-to-medium reduction to duration-deviants (Cohen’s d = 0.47). Together, this indicates that pitch-deviant MMN is not a candidate biomarker for schizophrenia prediction, while duration-deviant MMN may hold some promise, albeit nearly a third as large an effect as in chronic schizophrenia. Potential causes for discrepancies between studies are discussed.

In five experiments we measured the amplitude of the haemodynamic response to visual patterns using near infrared spectroscopy of the visual cortex. The patterns were gratings with bars that differed in chromaticity but not in luminance. In all experiments, with a wide range of chromaticities of the grating bars, the amplitude of the haemodynamic response increased with the separation of the chromaticities in the CIE 1976 UCS diagram. The amplitude did not vary consistently with the cone activation, or with the signal in colour difference channels. In four further experiments, again with a wide range of chromaticities, the gratings were rated for visual comfort. Discomfort increased consistently with the separation of the chromaticities. Given that a large haemodynamic response to patterns is generally associated with headache, we suggest that the discomfort may be a homeostatic signal to reduce sustained metabolic load on the visual cortex.

Mismatch negativity (MMN) is a robustly abnormal brainwave in chronically ill schizophrenia that has generated interest as a disease presence biomarker. Reports of MMN reduction in first-episode schizophrenia have been equivocal, raising uncertainty about its reduction at first psychotic break. Here we tested 29 schizophrenia-spectrum participants under 1 year from their first hospitalization for psychosis and 40 age-, gender-, parental socioeconomic status-, and Wechsler Adult Intelligence Scales III Information-matched healthy controls on both pitch and duration MMN. Participants performed a visual checkerboard tracking task while standard (1 kHz, 50 ms, 80%), pitch-deviant (1.2 kHz, 50 ms, 10%) and duration-deviant (1 kHz, 100 ms, 10%) tones were presented over headphones (75 dB) and EEG was recorded. Independent component analysis was used to remove eye movements and visual stimulus processing activity. Groups did not differ in pitch MMN or duration MMN amplitudes. Smaller pitch and duration MMN amplitudes were associated with lower estimates of premorbid intellect in all participants and independently with greater positive symptoms in first hospitalized schizophrenia. Overall MMN reduction was not present in these relatively high functioning individuals at the first episode of schizophrenia, and therefore is not a good disease presence biomarker for this sample. Future research is warranted to determine the degree of MMN reduction at the first episode of psychosis across a greater range of cognitive impairment, the utility of MMN as an indicator of risk or diagnosis, and its role for understanding pathophysiological mechanisms in emerging psychosis.

Background-Patients with migraine are averse to certain visual stimuli, such as flicker and striped patterns that evoke paroxysmal EEG activity in patients with photosensitive epilepsy. Migraineurs demonstrate a hyper-responsiveness to such stimuli, and there is debate as to whether the aversion and hyper-responsiveness are due to a hyperexcitability of the cortex similar to that in patients with photosensitive epilepsy. In these patients grating patterns with certain spatial characteristics can be epileptogenic, depending critically on their movement. If the contours of the grating drift continually, the grating is not epileptogenic, but if the contours are static or if their direction is repeatedly and rapidly reversed so as to vibrate, the grating then becomes highly epileptogenic.

Autism spectrum disorder (ASD) is characterized by a variety of social and non-social behavioral deficits. One potential mechanism that could unify this diverse profile of behaviors is slower processing speed. Seventy-six high-functioning adults with ASD were compared to 64 matched controls on standardized measures of processing speed. Participants with ASD were significantly slower on all measures, and on the composite score from the three tests (d's > .65). ASD participants with slower processing speeds scored higher on the ADOS Communication and Reciprocal Social Interaction scale (r = .34). These findings provide evidence of slower processing speeds in adults with ASD, and that this may be contributing to impairments in social communication skills. Interventions that improve processing speed might improve social communication abilities in ASD.

Mismatch negativity (MMN) in response to deviation from physical sound parameters (e.g., pitch, duration) is reduced in individuals with long-term schizophrenia (Sz), suggesting deficits in deviance detection. However, MMN can appear at several time intervals as part of deviance detection. Understanding which part of the processing stream is abnormal in Sz is crucial for understanding MMN pathophysiology. We measured MMN to complex pattern deviants, which have been shown to produce multiple MMNs in healthy controls (HC). Both simple and complex MMNs were recorded from 27 Sz and 27 matched HC. For simple MMN, pitch- and duration-deviants were presented among frequent standard tones. For complex MMN, patterns of five single tones were repeatedly presented, with the occasional deviant group of tones containing an extra sixth tone. Sz showed smaller pitch MMN (p=.009, ~110ms) and duration MMN (p=.030, ~170ms) than healthy controls. For complex MMN, there were two deviance-related negativities. The first (~150ms) was not significantly different between HC and SZ. The second was significantly reduced in Sz (p=.011, ~400ms). The topography of the late complex MMN was consistent with generators in anterior temporal cortex. Worse late MMN in Sz was associated with increased emotional withdrawal, poor attention, lack of spontaneity/conversation, and increased preoccupation. Late MMN blunting in schizophrenia suggests a deficit in later stages of deviance processing. Correlations with negative symptoms measures are preliminary, but suggest that abnormal complex auditory perceptual processes may compound higher-order cognitive and social deficits in the disorder.

Objective Individuals with migraine exhibit heightened sensitivity to visual input that continues beyond their migraine episodes. However, the contribution of color to visual sensitivity, and how it relates to neural activity, has largely been unexplored in these individuals. Background Previously, it has been shown that, in non‐migraine individuals, patterns with greater chromaticity separation evoked greater cortical activity, regardless of hue, even when colors were isoluminant. Therefore, to investigate whether individuals with migraine experienced increased visual sensitivity, we compared the behavioral and neural responses to chromatic patterns of increasing separation in migraine and non‐migraine individuals. Methods Seventeen individuals with migraine (12 with aura) and 18 headache‐free controls viewed pairs of colored horizontal grating patterns that varied in chromaticity separation. Color pairs were either blue‐green, red‐green, or red‐blue. Participants rated the discomfort of the gratings and electroencephalogram was recorded simultaneously. Results Both groups showed increased discomfort ratings and larger N1/N2 event‐related potentials (ERPs) with greater chromaticity separation, which is consistent with increased cortical excitability. However, individuals with migraine rated gratings as being disproportionately uncomfortable and exhibited greater effects of chromaticity separation in ERP amplitude across occipital and parietal electrodes. Ratings of discomfort and ERPs were smaller in response to the blue‐green color pairs than the red‐green and red‐blue gratings, but this was to an equivalent degree across the 2 groups. Conclusions Together, these findings indicate that greater chromaticity separation increases neural excitation, and that this effect is heightened in migraine, consistent with the theory that hyper‐excitability of the visual system is a key signature of migraine.