The human posterior cingulate and the stress-response benefits of viewing green urban landscapes.

The mechanistic and neural bases of why green environments drive positive mental health outcomes remain poorly understood. We show that viewing green urban landscapes that vary in terms of green-space density elicits corresponding changes in the activity of the human ventral posterior cingulate cortex that is correlated to behavioural stress-related responses. We further show that cingulate responses are engaged early in the processing cascade, influencing attentional and executive regions in a predominantly feedforward manner. Our data suggest a key role for this region in regulating (nature) dose-dependent changes in stress responses, potentially through its extensive connections to the prefrontal and hippocampal regions which in turn project towards the neuroendocrine system. As the posterior cingulate cortex is implicated in a variety of neurological diseases and disorders, these findings raise a therapeutic potential for natural environmental exposure, highlighting green-cover as a modifiable element that links to changes in limbic responses, and has health consequences for practitioners and city-planners alike.

The pontine-driven somatic gaze tract contributes to affective processing in humans.

The relevance of subcortical structures for affective processing is not fully understood. Inspired by the gerbil retino-raphe pathway that has been shown to regulate affective behavior and previous human work showing that the pontine region is important for processing emotion, we asked whether well-established tracts in humans traveling between the eye and the brain stem contribute to functions beyond their conventionally understood roles. Here we report neuroimaging findings showing that optic chiasm-brain stem diffusivity predict responses reflecting perceived arousal and valence. Analyses of subsequent task-evoked connectivity further revealed that visual affective processing implicates the brain stem, particularly the pontine region at an early stage of the cascade, projecting to cortico-limbic regions in a feedforward manner. The optimal model implies that all intrinsic connections between the regions of interest are unidirectional and outwards from the pontine region. These findings suggest that affective processing implicates regions outside the cortico-limbic network. The involvement of a phylogenetically older locus in the pons that has consequences in oculomotor control may imply adaptive consequences of affect detection.

Intraparietal stimulation disrupts negative distractor effects in human multi-alternative decision-making.

There has been debate about whether addition of an irrelevant distractor option to an otherwise binary decision influences which of the two choices is taken. We show that disparate views on this question are reconciled if distractors exert two opposing but not mutually exclusive effects. Each effect predominates in a different part of decision space: (1) a positive distractor effect predicts high-value distractors improve decision-making; (2) a negative distractor effect, of the type associated with divisive normalisation models, entails decreased accuracy with increased distractor values. Here, we demonstrate both distractor effects coexist in human decision making but in different parts of a decision space defined by the choice values. We show disruption of the medial intraparietal area (MIP) by transcranial magnetic stimulation (TMS) increases positive distractor effects at the expense of negative distractor effects. Furthermore, individuals with larger MIP volumes are also less susceptible to the disruption induced by TMS. These findings also demonstrate a causal link between MIP and the impact of distractors on decision-making via divisive normalisation.

Amygdala-pons connectivity is hyperactive and associated with symptom severity in depression.

Knowledge of the neural underpinnings of processing sad information and how it differs in people with depression could elucidate the neural mechanisms perpetuating sad mood in depression. Here, we conduct a 7 T fMRI study to delineate the neural correlates involved only in processing sad information, including pons, amygdala, and corticolimbic regions. We then conduct a 3 T fMRI study to examine the resting-state connectivity in another sample of people with and without depression. Only clinically depressed people demonstrate hyperactive amygdala-pons connectivity. Furthermore, this connectivity is related to depression symptom severity and is a significant indicator of depression. We speculate that visual sad information reinforces depressed mood and stimulates the pons, strengthening the amygdala-pons connectivity. The relationship between this connectivity and depressive symptom severity suggests that guiding one's visual attention and processing of sad information may benefit mood regulation.

Positive affect is inversely related to the salience and emotion network's connectivity.

Increasing evidence has shown that positive affect enhances many aspects of daily functioning. Yet, how dispositional positive affect is represented in the intrinsic brain networks remains unclear. Here, we used resting-state functional Magnetic Resonance Imaging to test how trait positive and negative affect of an individual were associated with the intrinsic connectivity of brain regions within the salience and emotion network and the default mode network in 70 healthy young adults. We observed that positive affect was negatively associated with connectivity within the salience and emotion network, particularly with the bidirectional connections spanning the left anterior insula and left nucleus accumbens. For connections between the salience and emotion network and the rest of the brain, we observed that positive affect was negatively related to the connectivity between the right amygdala and the right middle temporal gyrus. Affect-based modulations of connectivity were specific to positive affect and to the salience and emotion network. Our findings highlight the critical role of salience and emotion network in the neural relations of positive affect, and lay the groundwork for future studies on modeling the connectivity of salience and emotion network to predict mental well-being.