RESUMO
BACKGROUND: Aerobic endurance training has been discussed to induce brain plasticity and improve cognitive functions in healthy subjects and patients with neuropsychiatric disorders. For schizophrenia, a motor cortical inhibitory deficit has been established as one aspect of impaired plasticity, especially involving impairments in GABAergic interneuron networks, but the possibility to restore these deficits via exercise-induced plasticity has not been evaluated yet. METHODS: 17 schizophrenia patients and 16 matched healthy controls underwent 3 months of aerobic endurance training (30 min, 3 times a week) on bicycle ergometers. After 6 weeks, computer-assisted cognitive remediation training (30 min, 2 times a week) was added. Transcranial magnetic stimulation of the left and right hemispheres was performed at baseline and at the end of the intervention. We evaluated the intensity to induce a motor-evoked potential of 1 mV (S1mV), the resting motor threshold (RMT), the cortical silent period (CSP) at an intensity of 120 and 150% of the individual RMT, short-latency interval intracortical inhibition (3 ms), and intracortical facilitation (7 and 15 ms). Depending on the variable and hemisphere, follow-up data was available for 7-15 schizophrenia patients and for 10-12 healthy controls. RESULTS: Repeated measures ANOVA revealed no significant time × group interactions for any of the analyzed variables. A significant increase in S1mV and CSP duration at 150% RMT of the left hemisphere could be observed in both groups over time. CONCLUSION: Regular ergometer training over 3 months increases motor cortical inhibition as displayed by an increase in CSP. The increase in S1mV may also indicate a higher degree of inhibition after the intervention. We could not establish a difference between schizophrenia patients and healthy controls. Due to the limited sample size, our results have to be considered as preliminary and need to be replicated in future trials.
RESUMO
BACKGROUND: Impaired cortical inhibition is a well-established finding in schizophrenia patients and has been linked to dysfunctional gamma-aminobutyric acid (GABA)ergic transmission. However, there have been no previous studies investigating cortical excitability with particular regard to intracortical inhibitory networks in antipsychotic-naive subjects at risk of developing first-episode psychosis. METHODS: A total of 18 subjects at risk, 18 first-episode schizophrenia patients, and 18 healthy control subjects were included in this study. Transcranial magnetic stimulation over the left primary motor cortex was used to determine short-latency intracortical inhibition, intracortical facilitation, and the contralateral silent period (CSP). Short-latency intracortical inhibition can be considered as a parameter of GABA type A (GABA(A))-mediated inhibition and it has been proposed that CSP can test GABA type B (GABA(B))-mediated inhibitory intracortical networks. RESULTS: Subjects at risk and first-episode patients showed a reduced short-latency intracortical inhibition compared with healthy control subjects, suggesting reduced GABA(A)-mediated inhibition. First-episode patients had a prolonged CSP duration compared with the other two groups, implying a GABA(B) imbalance only in patients with full-blown psychosis. Analyses did not reveal group differences for intracortical facilitation. CONCLUSIONS: These results indicate specific alterations in inhibitory cortical networks in subjects at risk and in first-episode patients. It appears that there is already a cortical inhibitory deficit in at-risk individuals. These results suggest a possible GABA(A) dysfunction early in the disease course, whereas alterations in GABA(B) functionality seem to occur later in the disease's progression. Future longitudinal studies will be needed to clarify this inhibitory deficit and its relation to the transition to psychosis.
