Neurophysiological age differences during task-performance in a stereoscopic virtual environment

Action, observation or imitation of virtual hand movement affect differently regions of the mirror neuron system and the default mode network

Virtual reality (VR)-based paradigms use visual stimuli that can modulate visuo-motor networks leading to the stimulation of brain circuits. The aims of this study were to compare the changes in blood-oxygenation level dependent (BOLD) signal when watching and imitating moving real (RH) and virtual hands (VH) in 11 healthy participants (HP). No differences were found between the observation of RH or VH making this VR-based experiment a promising tool for rehabilitation protocols. VH-imitation involved more the ventral premotor cortex (vPMC) as part of the mirror neuron system (MNS) compared to execution and VH-observation conditions. The dorsal-anterior Precuneus (da-Pcu) as part of the Precuneus/posterior Cingulate Cortex (Pcu/pCC) complex, a key node of the Default Mode Network (DMN), was also less deactivated and therefore more involved. These results may reflect the dual visuo-motor roles for the vPMC and the implication of the da-Pcu in the reallocation of attentional and neural resources for bimodal task management. The ventral Pcu/pCC was deactivated regardless of the condition confirming its role in self-reference processes. Imitation of VH stimuli can then modulate the activation of specific areas including those belonging to the MNS and the DMN.

Beyond the real world: attention debates in auditory mismatch negativity

The aim of this study was to address the potential for the auditory mismatch negativity (aMMN) to be used in applied event-related potential (ERP) studies by determining whether the aMMN would be an attention-dependent ERP component and could be differently modulated across visual tasks or virtual reality (VR) stimuli with different visual properties and visual complexity levels. A total of 80 participants, aged 19-36 years, were assigned to either a reading-task (21 men and 19 women) or a VR-task (22 men and 18 women) group. Two visual-task groups of healthy young adults were matched in age, sex, and handedness. All participants were instructed to focus only on the given visual tasks and ignore auditory change detection. While participants in the reading-task group read text slides, those in the VR-task group viewed three 360° VR videos in a random order and rated how visually complex the given virtual environment was immediately after each VR video ended. Inconsistent with the finding of a partial significant difference in perceived visual complexity in terms of brightness of virtual environments, both visual properties of distance and brightness showed no significant differences in the modulation of aMMN amplitudes. A further analysis was carried out to compare elicited aMMN amplitudes of a typical MMN task and an applied VR task. No significant difference in the aMMN amplitudes was found across the two groups who completed visual tasks with different visual-task demands. In conclusion, the aMMN is a reliable ERP marker of preattentive cognitive processing for auditory deviance detection.

Neurophysiological handover from MMN to P3a in first-episode and recurrent major depression

BACKGROUND

Mismatch negativity (MMN) and P3a components are sequential and co-occur. MMN represents the pre-attentive index of deviance detection and P3a represents the attention orienting response. Major depressive disorder (MDD) is characterized by impaired pre-attentive information processing. To assess whether impaired pre-attentive information processing can lead to an impairment of subsequent orienting process as the neurophysiological transmission spreads from MMN to P3a in MDD.

METHODS

MMN/P3a was obtained during a two-tone auditory paradigm with 8% duration deviants in 45 first-episode major depression subjects (F-MD), 40 recurrent major depression subjects (R-MD), and 46 healthy controls (HC).

RESULTS

Compared with HC, F-MD and R-MD had lower MMN amplitudes and no differences were found between F-MD and R-MD. Notably, R-MD had lower P3a amplitudes and longer P3a latencies compared to HC, while F-MD had no differences. Interestingly, no correlations were found between the severity of depression and the deficits of MMN amplitude. The deficits of P3a amplitude, however, were negatively correlated with the severity of depression in F-MD and R-MD. Furthermore, the P3a amplitude deficits were positively correlated with the number of episodes in R-MD.

LIMITATIONS

Patients were on antidepressant medication.

CONCLUSIONS

The recurrence of depressive episodes can lead to impaired pre-attentive information processing, causing an impairment of subsequent orienting process as the neurophysiological transmission from MMN to P3a. It further suggests that the impaired processing indexed by MMN amplitude may be a stable trait biomarker for the appearance of depression, while P3a amplitude can be used a potential biomarker for recurrence.

Mismatch negativity/P3a complex in young people with psychiatric disorders: a cluster analysis

BACKGROUND

We have recently shown that the event-related potential biomarkers, mismatch negativity (MMN) and P3a, are similarly impaired in young patients with schizophrenia- and affective-spectrum psychoses as well as those with bipolar disorder. A data driven approach may help to further elucidate novel patterns of MMN/P3a amplitudes that characterise distinct subgroups in patients with emerging psychiatric disorders.

METHODS

Eighty seven outpatients (16 to 30 years) were assessed: 19 diagnosed with a depressive disorder; 26 with a bipolar disorder; and 42 with a psychotic disorder. The MMN/P3a complex was elicited using a two-tone passive auditory oddball paradigm with duration deviant tones. Hierarchical cluster analysis utilising frontal, central and temporal neurophysiological variables was conducted.

RESULTS

Three clusters were determined: the 'globally impaired' cluster (n = 53) displayed reduced frontal and temporal MMN as well as reduced central P3a amplitudes; the 'largest frontal MMN' cluster (n = 17) were distinguished by increased frontal MMN amplitudes and the 'largest temporal MMN' cluster (n = 17) was characterised by increases in temporal MMN only. Notably, 55% of those in the globally impaired cluster were diagnosed with schizophrenia-spectrum disorder, whereas the three patient subgroups were equally represented in the remaining two clusters. The three cluster-groups did not differ in their current symptomatology; however, the globally impaired cluster was the most neuropsychologically impaired, compared with controls.

CONCLUSIONS

These findings suggest that in emerging psychiatric disorders there are distinct MMN/P3a profiles of patient subgroups independent of current symptomatology. Schizophrenia-spectrum patients tended to show the most global impairments in this neurophysiological complex. Two other subgroups of patients were found to have neurophysiological profiles suggestive of quite different neurobiological (and hence, treatment) implications.

Delayed preattentional functioning in early psychosis patients with cannabis use

RATIONALE

Cannabis use is prevalent among the early psychosis (EP) population. The event-related potentials, mismatch negativity (MMN) and P3a are reduced in EP. Cannabinoids have been shown to modulate N-methyl-D-aspartate receptors which are involved in MMN generation.

OBJECTIVES

This study is the first to investigate the effects of cannabis use on MMN/P3a in EP.

METHODS

EP was defined as a history of psychosis or psychotic symptoms with no progression to date to chronic schizophrenia. Twenty-two EP patients with cannabis use (EP + CANN), 22 non-cannabis-using EP patients (EP-CANN) and 21 healthy controls participated in this study. MMN/P3a was elicited using a two-tone, auditory paradigm with 8% duration deviants.

RESULTS

As expected, EP-CANN showed marked reductions in MMN/P3a amplitudes compared to controls. However, EP + CANN showed evidence of a different pattern of neurophysiological expression of MMN/P3a compared to non-using patients, most notably in terms of delayed frontal MMN/P3a latencies.

CONCLUSIONS

This study provides further evidence that MMN/P3a deficits are present during early psychosis and suggests that this biomarker may have utility in differentiating substance- from non-substance-related psychoses.

MMN/P3a deficits in first episode psychosis: comparing schizophrenia-spectrum and affective-spectrum subgroups

BACKGROUND

Reduced mismatch negativity (MMN) and P3a amplitudes are neurophysiological biomarkers for schizophrenia that index deviance detection and the orienting response, respectively. First-episode psychosis (FEP) patients show reduced amplitudes of the 'MMN/P3a complex', but it is unclear whether this occurs across the FEP spectrum.

METHODS

Fifty-three young people (17-36 years) were assessed: 17 FEP affective-spectrum (bipolar disorder with psychotic features and major depressive disorder with psychotic features), 18 FEP schizophrenia-spectrum (schizophrenia, schizoaffective disorder, and schizophreniform disorder), and 18 healthy controls. MMN/P3a was acquired during a two-tone, auditory paradigm with 8% duration deviants. Clinical, psychosocial and neuropsychological assessments were also undertaken.

RESULTS

FEP schizophrenia- and FEP affective-spectrum showed significantly reduced fronto-central MMN and central P3a amplitudes compared to controls. FEP subgroups also showed significantly poorer cognitive and psychosocial functioning. The combined FEP sample showed significant correlations between fronto-central MMN amplitudes and cognitive measures.

DISCUSSION

FEP schizophrenia-spectrum and FEP affective-spectrum were similarly impaired in two biomarkers for schizophrenia. FEP subgroups showed impairments in fronto-central MMN consistent with chronic patients. Similarly, both subgroups showed reductions in P3a; although the affective subgroup showed an 'intermediate' frontal response. These findings suggest that FEP patients with both affective and schizophrenia spectrum diagnoses share common neurobiological disturbances in deviance detection/orienting processes in the early phase of illness.