Visual responses to reward-related cues in inferior parietal lobule

Neural substrates of motivational dysfunction across neuropsychiatric conditions: Evidence from meta-analysis and lesion network mapping

Motivational dysfunction constitutes one of the fundamental dimensions of psychopathology cutting across traditional diagnostic boundaries. However, it is unclear whether there is a common neural circuit responsible for motivational dysfunction across neuropsychiatric conditions. To address this issue, the current study combined a meta-analysis on psychiatric neuroimaging studies of reward/loss anticipation and consumption (4308 foci, 438 contrasts, 129 publications) with a lesion network mapping approach (105 lesion cases). Our meta-analysis identified transdiagnostic hypoactivation in the ventral striatum (VS) for clinical/at-risk conditions compared to controls during the anticipation of both reward and loss. Moreover, the VS subserves a key node in a distributed brain network which encompasses heterogeneous lesion locations causing motivation-related symptoms. These findings do not only provide the first meta-analytic evidence of shared neural alternations linked to anticipatory motivation-related deficits, but also shed novel light on the role of VS dysfunction in motivational impairments in terms of both network integration and psychological functions. Particularly, the current findings suggest that motivational dysfunction across neuropsychiatric conditions is rooted in disruptions of a common brain network anchored in the VS, which contributes to motivational salience processing rather than encoding positive incentive values.

Towards a neurocircuitry in anorexia nervosa: evidence from functional neuroimaging studies

Functional neuroimaging is widely used to unravel changes in brain functioning in psychiatric disorders. In the current study, we review single-photon emission tomography (SPECT), positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) studies in anorexia nervosa (AN), a difficult-to-treat eating disorder with the highest mortality rate among psychiatric disorders. We discuss the role of the parietal cortex, anterior and subgenual cingulate cortex, frontal cortex and temporal lobe in light of the cardinal symptoms of AN. The insights of the current review may ultimately lead to the development of new treatments.

Hunger and satiety in anorexia nervosa: fMRI during cognitive processing of food pictures

Neuroimaging studies of visually presented food stimuli in patients with anorexia nervosa have demonstrated decreased activations in inferior parietal and visual occipital areas, and increased frontal activations relative to healthy persons, but so far no inferences could be drawn with respect to the influence of hunger or satiety. Thirteen patients with AN and 10 healthy control subjects (aged 13-21) rated visual food and non-food stimuli for pleasantness during functional magnetic resonance imaging (fMRI) in a hungry and a satiated state. AN patients rated food as less pleasant than controls. When satiated, AN patients showed decreased activation in left inferior parietal cortex relative to controls. When hungry, AN patients displayed weaker activation of the right visual occipital cortex than healthy controls. Food stimuli during satiety compared with hunger were associated with stronger right occipital activation in patients and with stronger activation in left lateral orbitofrontal cortex, the middle portion of the right anterior cingulate, and left middle temporal gyrus in controls. The observed group differences in the fMRI activation to food pictures point to decreased food-related somatosensory processing in AN during satiety and to attentional mechanisms during hunger that might facilitate restricted eating in AN.

Simple spike firing in the posterior lateral cerebellar cortex of Macaque Mulatta was correlated with success-failure during a visually guided reaching task

Evidence has been accumulating which supports a role for the cerebellum in motor learning. Motor learning is though to be mediated by complex spikes acting as an error signal, which when firing in conjunction with simple spike activity modify synapses between parallel fibers and Purkinje cells. We studied the activity of neurons in the posterior lateral cerebellar cortex of macaques that were performing reaches to visual targets. We found that simple spike firing in many of these neurons was modulated by whether the monkey successfully hit the target or not. The success-failure modulation was present for reaches using either arm and could persist for several hundred milliseconds into a period when the monkey was constrained from moving its arms. This temporally extended success-failure activity could interact with complex spike firing in order to enhance learning, particularly when the motor command is temporally separated from sensory feedback.

Attention and memory trials during neuronal recording from the primate pulvinar and posterior parietal cortex (area PG)

Cynomolgus monkeys were trained on a delayed match-to-sample (DMS) task. Several controls were performed for the separation of memory effects from other factors such as attention, stimulus attributes and eye movements. One of the controls employed a standardised sequence of events ('window trial') during which a window in a black screen was opened and a face, an object or a picture was presented. Unit cell activity was recorded from 209 sites in the posterior parietal cortex (area PG) and 186 sites in the pulvinar. Some units responded during the presentation of the DMS stimuli, mostly those in that part of area PG located in the superior temporal sulcus. They often appeared to be related to the task-related state of attention. There was no indication of pure memory-related changes in activity such as sustained responses during the inter-stimulus interval or specific responses to the second stimulus that would indicate a dependence on the kind of the preceding stimulus. In the window trial, some parietal units, mostly in that part of area PG located in the intraparietal sulcus (a region termed area LIP), responded in a relatively specific manner during and sometimes even after, the presentation of a human face. The responses often seemed to be related to the animal's state of attention. Almost no pulvinar unit responded in this paradigm. It is concluded that area PG and, to a lesser extent, the pulvinar are involved in the modulation of attention in relation to behaviourally relevant changes in the environment. If these structures have a role in memory function, it must be secondary to a role in controlling or regulating attention.