No description available.

No description available.

Feeding behavior is a complex phenomenon involving homeostatic signals, and non-homeostatic inputs such as visual cues. In primates, exposure to food-related sensory cues has been shown to elicit cephalic phase responses as well as trigger central appetitive processing, in a motivationally-dependent manner. Neural structures consistently implicated in such responses and/or in the regulation of ingestive behavior in general, in both monkeys and in humans, include the amygdala, insula, striatum, hypothalamus, and frontal and occipital cortices. In humans however, the cerebral response to visual food stimulation remains minimally explored. / Functional Magnetic Resonance Imaging (fMRI) provides information about state-dependent changes in local neuronal activity in vivo. Using fMRI, the present dissertation examined changes in human brain activity to food and nonfood pictures following the pharmacological induction of hunger with the orexigenic hormone ghrelin (Study 1), and following manipulation of the cognitive state of food expectation (Study 2). / Our data reinforce the involvement of a distributed frontal-limbic-paralimbic circuit in the central processing of food imagery, under both experimental conditions. The first study revealed that intravenous ghrelin administration potently modulated food-associated neural responses III areas involved in reward, motivation, memory, and attention (amygdala, insula, orbitofrontal cortex, striatum, hippocampus, midbrain, visual areas). This suggests that metabolic signals such as ghrelin may promote food consumption by enhancing the appetitive response to food cues via engagement of the hedonic network. / The second study revealed that brain regions activated in the 'expectant' state (i.e. when subjects were anticipating food reward) were at least partially dissociable from those in the 'not expectant' state. In particular, recruitment of the dorsolateral prefrontal cortex, a principal component in the cognitive control network, exclusively in the 'not expectant' condition, may signal an attempt to suppress appetite in the absence of food expectation. Areas of convergence were observed in the amygdala and insula. / Obesity is rapidly becoming the major cause of excess mortality worldwide; therefore, understanding how the central nervous system controls appetite and nutrient consumption is of considerable interest. The projects in this thesis offer significant insights regarding the effects two select factors (one intrinsic and the other extrinsic) on the neural reaction to visual food stimuli, in healthy male participants.

Motor response selection is the process by which an intention to act is transformed into an action; this multifaceted process occurs at the interface between cognitive and motor systems. Despite the importance of response selection, the nature and neural implementation of this process is still a subject of debate (Thompson-Schill et al, 1997; Botvinick et al., 2001; Rushworth et al., 2004; Nachev et al., 2007). While previous research has demonstrated that the selection of finger movements relies on a distributed network involving premotor and prefrontal areas, the specific contribution of these regions, however, remains unclear. It is also unclear if the selection of words engages similar processes as the selection of finger movements, that is, if response selection is a domain-general or a domain-specific process. In order to address these issues, a set of four complementary studies using functional magnetic resonance imaging (fMRI) and repetitive transcranial magnetic stimulation (rTMS) was developed in which different factors affecting response selection were examined: selection mode, response type (words vs. oral movements), attention and response competition (conflict). / The results of these studies provide new insights into the neural architecture of response selection by uncovering the respective contribution of premotor areas (pre-SMA and PMA) and prefrontal areas (DLPFC and IFG). A preliminary two-stage model of response selection is proposed, in which the PMA is generating a set of response alternatives from which the pre-SMA performs selection using one of two different mechanisms (response facilitation and response inhibition). In general, these findings do not support the hypothesis of a medio-lateral gradient of control (Goldberg, 1985) but confirm the fundamental role of the lateral (PMA) and medial (pre-SMA) premotor areas in the process of selecting motor responses. / Importantly, the results also demonstrate that selection is a domain-general (response-independent) process. Uncovering the general, multifaceted nature of brain mechanisms is essential to reveal the basic units of control in the central nervous system; this knowledge is fundamental to broaden current understanding of the basic brain operations that are used to produce language. Theoretical and clinical implications of these findings are discussed.

No description available.

Prenatal maternal stress and mood, and early postnatal mother-infant interactions set the stage for the child’s psychobiological, neurological and social development. While a large body of research connecting maternal depression to infant EEG asymmetry exists, the current study sought to add to the sparse literature on maternal anxiety and infant EEG. Mother-infant dyads were assessed prenatally during the third trimester, soon after birth, at 6 weeks and 3 months postnatal. Association between maternal depression and later development of right mid-frontal alpha asymmetry was confirmed, while trends suggested maternal anxiety may be associated with lateral frontal alpha asymmetry. Greater maternal sensitivity and anxiety were each associated with lower post-stressor cortisol in infants with right frontal asymmetry. Greater time spent in mutual gaze was associated with positive infant affect. Finally, quality mother-infant dynamics encourage positive infant affect and healthy physiological stress regulation even when brain patterns associated with dysregulation have been established. / Includes bibliography. / Thesis (M.A.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection