Structural brain abnormalities in schizophrenia in adverse environments: examining the effect of poverty and violence in six Latin American cities.

BACKGROUND: Social and environmental factors such as poverty or violence modulate the risk and course of schizophrenia. However, how they affect the brain in patients with psychosis remains unclear. AIMS: We studied how environmental factors are related to brain structure in patients with schizophrenia and controls in Latin America, where these factors are large and unequally distributed. METHOD: This is a multicentre study of magnetic resonance imaging in patients with schizophrenia and controls from six Latin American cities. Total and voxel-level grey matter volumes, and their relationship with neighbourhood characteristics such as average income and homicide rates, were analysed with a general linear model. RESULTS: A total of 334 patients with schizophrenia and 262 controls were included. Income was differentially related to total grey matter volume in both groups (P = 0.006). Controls showed a positive correlation between total grey matter volume and income (R = 0.14, P = 0.02). Surprisingly, this relationship was not present in patients with schizophrenia (R = -0.076, P = 0.17). Voxel-level analysis confirmed that this interaction was widespread across the cortex. After adjusting for global brain changes, income was positively related to prefrontal cortex volumes only in controls. Conversely, the hippocampus in patients with schizophrenia, but not in controls, was relatively larger in affluent environments. There was no significant correlation between environmental violence and brain structure. CONCLUSIONS: Our results highlight the interplay between environment, particularly poverty, and individual characteristics in psychosis. This is particularly important for harsh environments such as low- and middle-income countries, where potentially less brain vulnerability (less grey matter loss) is sufficient to become unwell in adverse (poor) environments.

Attending to the heart is associated with posterior alpha band increase and a reduction in sensitivity to concurrent visual stimuli.

Attentional mechanisms have been studied mostly in specific sensory domains, such as auditory, visuospatial, or tactile modalities. In contrast, attention to internal interoceptive visceral targets has only recently begun to be studied, despite its potential importance in emotion, empathy, and self-awareness. Here, we studied the effects of shifting attention to the heart using a cue-target detection paradigm during continuous EEG recordings. Subjects were instructed to count either a series of visual stimuli (visual condition) or their own heartbeats (heart condition). Visual checkerboard stimuli were used as attentional probes throughout the task. Consistent with previous findings, attention modulated the amplitude of the heartbeat-evoked potentials. Directing attention to the heart significantly reduced the visual P1/N1 amplitude evoked by the attentional probe. ERPs locked to the attention-directing cue revealed a novel frontal positivity around 300 ms postcue. Finally, spectral power in the alpha band over parieto-occipital regions was higher while attending to the heart-when compared to the visual task-and correlated with subject's performance in the interoceptive task. These results are consistent with a shared, resource-based attentional mechanism whereby allocating attention to bodily signals can affect early responses to visual stimuli.