Biomedical subjects

B Gulyas

Publications and source records attributed to B Gulyas.

6 recordsLinked to original sources

PubMed2001

Smelling of odorous sex hormone-like compounds causes sex-differentiated hypothalamic activations in humans.

The anatomical pathways for processing of odorous stimuli include the olfactory nerve projection to the olfactory bulb, the trigeminal nerve projection to somatosensory and insular cortex, and the projection from the accessory olfactory bulb to the hypothalamus. In the majority of tetrapods, the sex-specific effects of pheromones on reproductive behavior is mediated via the hypothalamic projection. However, the existence of this projection in humans has been regarded as improbable because humans lack a discernable accessory olfactory bulb. Here, we show that women smelling an androgen-like compound activate the hypothalamus, with the center of gravity in the preoptic and ventromedial nuclei. Men, in contrast, activate the hypothalamus (center of gravity in paraventricular and dorsomedial nuclei) when smelling an estrogen-like substance. This sex-dissociated hypothalamic activation suggests a potential physiological substrate for a sex-differentiated behavioral response in humans.

Adult↗

PubMed2001

Brain activation during odor perception in males and females.

Several studies indicate that women outperform men in olfactory identification tasks. The psychophysical data are more divergent when it comes to gender differences at levels of odor processing which are cognitively less demanding. We therefore compared cerebral activation with H2(15)O PET in 12 females and 11 males during birhinal passive smelling of odors and odorless air. The odorous compounds (odorants) were pure olfactory, or mixed olfactory and weakly trigeminal. Using odorless air as the baseline condition, activations were found bilaterally in the amygdala, piriform and insular cortices in both sexes, irrespective of the odor. No gender difference was detected in the pattern of cerebral activation (random effect analysis SPM99, corrected p < 0.05) or in the subjective perception of odors. Males and females seem to use similar cerebral circuits during the passive perception of odors. The reported female superiority in assessing olfactory information including odor identification is probably an effect of a difference at a cognitive, rather than perceptive level of olfactory processing.

Adult↗

PubMed2000

PET shows that odors are processed both ipsilaterally and contralaterally to the stimulated nostril.

The olfactory nerve is the only cranial nerve with established ipsilateral primary cerebral anatomical projections. Whether these projections correspond to the functional pathways for monorhinal processing of odor perception is, however, unknown. We therefore studied cerebral blood flow (rCBF) with [15O]butanol-PET in 18 healthy females during monorhinal smelling of single odors (OS) and odorless air (AS). Compared with AS, OS activated right amygdala and piriform cortex (confluent cluster), right orbitofrontal cortex, left insula, right thalamus, and anterior cingulate. A post hoc analysis showed that the first three regions were activated independently of the stimulated side, but that right orbitofrontal rCBF was higher during the right nostril stimulations. Left insula was activated mainly by the right nostril stimuli, and right thalamus by the left nostril stimuli. Odors seem to be processed both ipsi and contralaterally, with a right hemisphere preponderance irrespective of the stimulated nostril.

Adult↗

PubMed2000

Olfactory functions are mediated by parallel and hierarchical processing.

How the human brain processes the perception, discrimination, and recognition of odors has not been systematically explored. Cerebral activations were therefore studied with PET during five different olfactory tasks: monorhinal smelling of odorless air (AS), single odors (OS), discrimination of odor intensity (OD-i), discrimination of odor quality (OD-q), and odor recognition memory (OM). OS activated amygdala-piriform, orbitofrontal, insular, and cingulate cortices and right thalamus. OD-i and OD-q both engaged left insula and right cerebellum. OD-q also involved other areas, including right caudate and subiculum. OM did not activate the insula, but instead, the piriform cortex. With the exception of caudate and subiculum, it shared the remaining activations with the OD-q, and engaged, in addition, the temporal and parietal cortices. These findings indicate that olfactory functions are organized in a parallel and hierarchical manner.

Adult↗

PubMed1998

Regional increases in [11C]flumazenil binding after epilepsy surgery.

INTRODUCTION: Animal experiments suggest that epileptic seizures alter the expression of mRNA for neuro-receptors. PET measurements with [11C]flumazenil show that patients with partial seizures have a reduced density of benzodiazepine (BZ) receptors in the epileptogenic regions (ER) and some of the target areas for seizure activity, the so called projection areas. Recent data suggest that the degree of BZ receptor reduction in ER is correlated to seizure frequency. We therefore hypothesized that seizure activity can alter the BZ receptor binding, and that some of these changes could normalize when the seizures disappeared. METHODS: In 4 patients whose seizures were generated by mesial temporal lobe structures, BZ receptor density was measured with [11C]flumazenil PET before, and 1 year after the epilepsy surgery and cessation of seizures. By use of a computerized anatomical brain atlas the same regions were analyzed in both PET scans, and the results related to data from 7 healthy controls. RESULTS: Presurgical PET scans showed reductions in BZ receptor density in the epileptogenic region and some of its primary projection areas. Other cortical regions had normal values. Postsurgically, the calculated BZ receptor density normalized (29+/-17% increase) in several of the affected projection areas, whereas the values in other cortical regions remained unaltered. CONCLUSION: Regional reductions in BZ receptor density may be dynamic and related to seizures. The present preliminary observations encourage further studies on seizure-related changes in regional receptor binding in humans.

Adult↗

PubMed1989

Laminar analysis of motion information processing in macaque V5.

Although it has been repeatedly shown that properties of striate cells depend on laminar position, no information is available about the vertical organization of primate extrastriate cortex. Laminar analysis in the part of macaque V5 (the middle temporal visual area) devoted to the central 10 degrees in the visual field, reveals that interaction between a moving bar and a moving texture differs systematically between layers. We found that cells for which the direction selectivity does not depend on texture motion occur mainly in layer 4 and in the infragranular layers. Cells with only pseudomodulation of direction selectivity were found throughout the cortical depth. Cells for which direction selectivity was abolished when both patterns moved inphase occur outside layer 4 and therefore represent a higher processing stage. These 3 types differ not only in laminar position but also in velocity selectivity and in strength of texture response. These findings suggest that the 3 classes represent distinct physiological types of neurons dedicated to different stages of motion processing which takes place in V5, and suggest that these cells may play different roles in the guidance of eye movements.

Animals↗