GABA levels in the ventromedial prefrontal cortex during the viewing of appetitive and disgusting food images

Abstract

Characterizing how the brain appraises the psychological dimensions of reward is one of the central topics of neuroscience. It has become clear that dopamine neurons are implicated in the transmission of both rewarding information and aversive and alerting events through two different neuronal populations involved in encoding the motivational value and the motivational salience of stimuli, respectively. Nonetheless, there is less agreement on the role of the ventromedial prefrontal cortex (vmPFC) and the related neurotransmitter release during the processing of biologically relevant stimuli. To address this issue, we employed magnetic resonance spectroscopy (MRS), a non-invasive methodology that allows detection of some metabolites in the human brain in vivo, in order to assess the role of the vmPFC in encoding stimulus value rather than stimulus salience. Specifically, we measured gammaaminobutyric acid (GABA) and, with control purposes, Glx levels in healthy subjects during the observation of appetitive and disgusting food images. We observed a decrease of GABA and no changes in Glx concentration in the vmPFC in both conditions. Furthermore, a comparatively smaller GABA reduction during the observation of appetitive food images than during the observation of disgusting food images was positively correlated with the scores obtained to the body image concerns sub-scale of Body Uneasiness Test (BUT). These results are consistent with the idea that the vmPFC plays a crucial role in processing both rewarding and aversive stimuli, possibly by encoding stimulus salience through glutamatergic and/or noradrenergic projections to deeper mesencephalic and limbic areas.

Number of subjects required in common study designs for functional GABA magnetic resonance spectroscopy in the human brain at 3 Tesla

“…This is an important finding for studies that hypothesise a low concentration change in GABA. However, for an effect size of around 15%, we predict much more reasonable sample sizes (between 8 and 43 depending on the region, excluding the LMC) which is evidenced by recent literature (Cleve et al, ; Padulo et al, ). The power calculations in this paper are limited to only six regions in the brain; however, it is logical to assume a similar behaviour in adjacent regions with similar spectra quality.…”

“…The number of subjects required to detect a 15% change of GABA concentration in each region of interest is reported in Table for each region, study design and duration investigated (assuming a standard voxel size of 27 cm 3 ). Here, we use 15% as an illustration based on a number of previous studies who have found a change in GABA in this range in response to intervention, for example (Cleve et al, ; Padulo et al, ). As expected it can be observed that for the same effect size, a larger number of subjects is required for between‐group studies compared to a within‐session study, and the longer the acquisition time, the fewer subjects that are needed.…”

The locus coeruleus–norepinephrine system as pacemaker of attention – a developmental mechanism of derailed attentional function in autism spectrum disorder

“…The ACC and AI supported attentional control by deactivating the default mode network (Seeley et al ., ; Sridharan et al ., ). The vmPFC primarily compares sensory input to motivational states (Padulo et al ., ). Attentional control causes sustained phasic LC–NE activity that maintains alerting and orienting (Aston‐Jones & Cohen, ) and results in increased between‐network functional connectivity (Sara, ; Gilzenrat et al ., ; Mückschel et al ., ; Berry et al ., ).…”

Rehabilitation program based on sensorimotor recovery improves the static and dynamic balance and modifies the basal ganglia neurochemistry

“…In depth, using spectra without water suppression, we determined the area of the water peak and utilized it as an internal standard reference for tCr quantification. [ 22 – 27 ]…”