Biomedical subjects

Fernando Zelaya

Publications and source records attributed to Fernando Zelaya.

4 recordsLinked to original sources

PubMed2006

Probing the working memory system in chronic fatigue syndrome: a functional magnetic resonance imaging study using the n-back task.

OBJECTIVE: Up to 90% of patients with chronic fatigue syndrome (CFS) report substantial cognitive difficulties. However, objective evidence supporting these claims is inconsistent. The present functional magnetic resonance imaging study examined the neural correlates of working memory in patients with CFS compared with controls. METHODS: Seventeen patients with CFS and 12 healthy control subjects were scanned while performing a parametric version of the n-back task (0-, 1-, 2-, and 3-back). RESULTS: Both groups performed comparably well and activated the verbal working memory network during all task levels. However, during the 1-back condition, patients with CFS showed greater activation than control subjects in medial prefrontal regions, including the anterior cingulate gyrus. Conversely, on the more challenging conditions, patients with CFS demonstrated reduced activation in dorsolateral prefrontal and parietal cortices. Furthermore, on the 2- and 3-back conditions, patients but not control subjects significantly activated a large cluster in the right inferior/medial temporal cortex. Trend analyses of task load demonstrated statistically significant differences in brain activation between the two groups as the demands of the task increased. CONCLUSIONS: These results suggest that patients with CFS show both quantitative and qualitative differences in activation of the working memory network compared with healthy control subjects. It remains to be determined whether these findings stay stable after successful treatment.

Adult↗

PubMed2003

Neural correlates of anxiety associated with obsessive-compulsive symptom dimensions in normal volunteers.

BACKGROUND: The neural correlates of anxiety associated with obsessive-compulsive symptomlike provocation in normal volunteers are unknown. METHODS: Ten healthy volunteers participated in four functional magnetic resonance experiments. Subjects were scanned while viewing alternating blocks of emotional (normally aversive, washing-relevant, checking-relevant, or hoarding-relevant pictures) and neutral pictures, and imagining scenarios related to the content of each picture type. Nonparametric brain mapping analyses were used. RESULTS: In response to the provocative pictures in all experiments, increases in subjective anxiety and activation in bilateral ventral prefrontal, limbic, dorsal prefrontal, and visual regions were demonstrated. Anxiety related to different symptom dimensions was associated with different patterns of activation: provocation of washing-relevant anxiety predominantly activated dorsal and ventral prefrontal regions; checking-relevant anxiety predominantly activated dorsal prefrontal regions; and hoarding-relevant anxiety predominantly activated ventral prefrontal regions and the left amygdala. CONCLUSIONS: Our findings support a dimensional model of obsessive-compulsive disorder (OCD) whereby 1) the brain systems implicated in the mediation of anxiety in response to symptom-related material in normal subjects are similar to those identified in OCD patients during symptom provocation, and 2) anxiety associated with different symptom dimensions is associated with differential patterns of activation of these neural systems. Further investigation of the neural basis of OCD symptom dimensions is required.

Adult↗

PubMed2003

The effect of negative emotional context on neural and behavioural responses to oesophageal stimulation.

Sensory experience is influenced by emotional context. Although perception of emotion and unpleasant visceral sensation are associated with activation within the insula and dorsal and ventral anterior cingulate gyri (ACG), regions important for attention to and perception of sensory and emotional information, the neural mechanisms underlying the effect of emotional context upon visceral sensation remain unexplored. Using functional MRI, we examined neural responses to phasic, non-painful oesophageal sensation (OS) in eight healthy subjects (seven male; age range 27-36 years) either during neutral or negative emotional contexts produced, respectively, by presentation of neutral or fearful facial expressions. Activation within right insular and bilateral dorsal ACG was significantly greater (P < 0.01) during OS with fearful than with neutral faces. In a second experiment, we measured anxiety, discomfort and neural responses in eight healthy male subjects (age range 22-41 years) to phasic, non-painful OS during presentation of faces depicting either low, moderate or high intensities of fear. Significantly greater (P < 0.01) discomfort, anxiety and activation predominantly within the left dorsal ACG and bilateral anterior insulae occurred with high-intensity compared with low-intensity expressions. Clusters of voxels were also detected in this region, which exhibited a positive correlation between subjective behaviour and blood oxygenation level-dependent effect (P < 0.05). We report the first evidence for a modulation of neural responses, and perceived discomfort during, non-painful visceral stimulation by the intensity of the negative emotional context in which the stimulation occurs, and suggest a mechanism for the effect of negative context on symptoms in functional pain disorders.

Adult↗

PubMed2003

Practice and difficulty evoke anatomically and pharmacologically dissociable brain activation dynamics.

Brain activation is adaptive to task difficulty and practice. We used functional MRI to map brain systems activated by an object-location learning task in 24 healthy elderly volunteers each scanned following placebo and two of four active drugs studied. We distinguished a fronto-striatal system adaptive to difficulty from a posterior system adaptive to practice. Fronto-striatal response to increased cognitive load was significantly attenuated by scopolamine, sulpiride and methylphenidate; practice effects were not modulated by these drugs but were enhanced by diazepam. We also found enhancement by methylphenidate, and attenuation by sulpiride, of load response in premotor, cingulate and parietal regions comprising a spatial attention network. Difficulty and practice evoke anatomically and pharmacologically dissociable brain activation dynamics, which are probably mediated by different neurotransmitter systems in humans.

Adrenergic Uptake Inhibitors↗