Csaba Szalay

History of simple febrile seizures is associated with hippocampal abnormalities in adults

Background: It is unclear whether the hippocampal abnormality in temporal lobe epilepsy (TLE) is a consequence or the cause of afebrile or febrile seizures (FSs). We investigated whether hippocampal abnormalities are present in healthy adults > 15 years after a simple FS.

Gustatory perception alterations in obesity: An fMRI study

The background of feeding associated and metabolic diseases is not sufficiently understood yet. Since gustatory alterations may be of particular significance in the above illnesses, in the present experiments, cerebral activation was detected by fMRI in twelve obese patients and twelve, age and gender matched healthy subjects. The gustatory stimulus solutions were delivered via intraorally positioned polyvinyl tubes. Each session consisted of three runs. Sucrose was used as a pleasant; quinine HCl as an aversive; and a high-calorie, vanilla flavored nourishment solution as a complex taste of high palatability. In each run, only one taste was used as a stimulus. During all runs, distilled water served as a neutral stimulus. Group analysis was made by using the FSL software package. The taste stimuli elicited characteristic and distinct activity changes of the two groups. In contrast to the controls, in the obese patients, stronger activation was detected in various cortical (anterior cingulate cortex, insular and opercular cortices, orbitofrontal cortex) and subcortical (amygdala, nucleus accumbens, putamen and pallidum) structures in case of all three stimuli. The present examinations elucidated differential activation of various brain structures to pleasant and unpleasant gustatory stimuli in obese patients compared to control subjects. These taste alterations are supposed to be of particular significance in obesity, and our findings may contribute to develop better strategies for prevention and effective therapies in the future.

Glucose-monitoring neurons in the nucleus accumbens.

The nucleus accumbens, a key structure of the limbic circuitry, is involved in the regulation of motivated behaviors. The accumbens performs its roles via interconnections with brain areas where glucose-monitoring neurons have been localized. To search for such integrative chemosensory cells here, extracellular single neuron activity was recorded in the nucleus accumbens of Wistar rats by means of multibarreled glass microelectrodes during microelectrophoretic administration of D-glucose and other chemicals. Every fourth neuron tested changed in activity in response to glucose. Accumbens cells also displayed distinct &ggr;-amino-n-butyric acid type sensitivity. It is suggested that differential distribution of the chemosensory units, demonstrated between subdivisions of the nucleus accumbens, has particular significance with respect to functional dichotomy of the shell and core subregions.

Right–left discrimination is related to the right hemisphere

We aimed to determine the functional localisation of right–left discrimination (RLD) by functional MRI (fMRI). In this study, 16 male volunteers were examined. There were three task sessions: one active and two baseline tasks. During the baseline tasks participants were instructed to show numbers with their fingers. The first baseline task was performed with the right hand, the second one with the left hand. During the active (RLD) task participants were also instructed to show numbers. The difference between baseline and active tasks was that during the active task the hand with which the participant should perform the instruction was assigned randomly. Thus, participants were unaware which hand should be used before the instruction command. During RLD, activations occurred in the right-sided frontal, precuneus, postcentral, angular, lingual, and superior temporal gyri. Activations also appeared in the left-sided temporal gyri and precuneus. Of the activations, 76.7% appeared in the right hemisphere, 23.3% in the left hemisphere. Conclusively, we found that RLD is mainly related to the right hemisphere, and requires activation of the parieto-temporo-occipital junction and the visual system including cuneus, precuneus, and gyrus lingualis.

Homeostatic alterations after IL-1β microinjection into the nucleus accumbens of the rat

The present study investigates the effects of direct administration of interleukin-1beta (IL-1beta) into the nucleus accumbens (NAcc) on homeostatic regulation. Short- and long-term food intakes (FI), water intakes (WI) and body temperature (BT) were measured before and after bilateral microinjection of IL-1beta (with or without paracetamol pretreatment) into the NAcc of Wistar rats, and the effects were compared with those found in vehicle treated control animals. In addition, blood glucose levels, along with a glucose tolerance test (GTT), and plasma concentrations of metabolic parameters, such as total cholesterol, triglycerides, HDL, LDL and uric acid were determined in cytokine treated and control rats. Short-term FI and WI were suppressed after intraaccumbens application of IL-1beta. A significant increase of BT was also observed after the cytokine microinjection. Pretreatment with paracetamol failed to influence the anorexigenic, adipsogenic, and pyrogenic effects of IL-1beta. A definite glucose intolerance of the cytokine treated animals and their pathologically elevated blood glucose levels became obvious in the acute GTT. Following IL-1beta microinjection, plasma levels of triglycerides, total cholesterol and LDL were found increased. Our present findings show that the NAcc is an important site of action of IL-1beta mediated processes in central homeostatic regulation.

Glucose-monitoring neurons in the mediodorsal prefrontal cortex

The mediodorsal prefrontal cortex (mdPFC), a key structure of the limbic neural circuitry, plays important roles in the central regulation of feeding. As an integrant part of the forebrain dopamine (DA) system, it performs complex roles via interconnections with various brain areas where glucose-monitoring (GM) neurons have been identified. The main goal of the present experiments was to examine whether similar GM neurons exist in the mediodorsal prefrontal cortex. To search for such chemosensory cells here, and to estimate their involvement in the DA circuitry, extracellular single neuron activity of the mediodorsal prefrontal cortex of anesthetized Wistar and Sprague-Dawley rats was recorded by means of tungsten wire multibarreled glass microelectrodes during microelectrophoretic administration of d-glucose and DA. One fourth of the neurons tested changed in firing rate in response to glucose, thus, proved to be elements of the forebrain GM neural network. DA responsive neurons in the mdPFC were found to represent similar proportion of all cells; the glucose-excited units were shown to display excitatory whereas the glucose-inhibited neurons were demonstrated to exert mainly inhibitory responses to dopamine. The glucose-monitoring neurons of the mdPFC and their distinct DA sensitivity are suggested to be of particular significance in adaptive processes of the central feeding control.

Lateralisation of non-metric rhythm.

There are contradictory results on lateralisation and localisation of rhythm processing. Our aim was to test whether there is a hemispheric dissociation of metric and non-metric rhythm processing. We created a non-metric rhythm stimulus without a sense of metre and we measured brain activities during passive rhythm perception. A total of 11 healthy, right-handed, native female Hungarian speakers aged 21.3 ± 1.1 were investigated by functional magnetic resonance imaging (fMRI) using a 3T MR scanner. The experimental acoustic stimulus consisted of comprehensive sentences transformed to Morse code, which represent a non-metric rhythm with irregular perceptual accent structure. Activations were found in the right hemisphere, in the posterior parts of the right-sided superior and middle temporal gyri and temporal pole as well as in the orbital part of the right inferior frontal gyrus. Additional activation appeared in the left-sided superior temporal region. Our study suggests that non-metric rhythm with irregular perceptual accents structure is confined to the right hemisphere. Furthermore, a right-lateralised fronto-temporal network extracts the continuously altering temporal structure of the non-metric rhythm.

Quantitative proton MRI and MRS of the rat brain with a 3 T clinical MR scanner

OBJECTIVE To demonstrate the capability of a clinical 3T human scanner in performing quantitative MR experiments in the rat brain. MATERIAL AND METHODS In vivo, measurements on eight Wistar rats were performed. Longitudinal relaxation time (T1) and transverse relaxation time (T2) measurements were set up at a spatial resolution of 0.3×0.3×1mm(3). Diffusion-weighted imaging was also applied and the evaluation included both mono- and biexponential approaches (b-value up to 6000s/mm(2)). Besides quantitative imaging, the rat brain was also scanned at a microscopic resolution of 130×130×130μm(3). Quantitative proton spectroscopy was also carried out on the rat brain with water as internal reference. RESULTS T1 and T2 for the rat brain cortex were 1272±85ms and 75±2ms, respectively. Diffusion-weighted imaging yielded accurate diffusion coefficient measurements at both low and high b-value ranges. The concentrations of MR visible metabolites were determined for the major resonances (i.e., N-acetyl-aspartate, choline and creatine) with acceptable accuracy. CONCLUSION The results suggest that quantitative imaging and spectroscopy can be carried out on small animals on high-field clinical scanners.

Taste reactivity deficit in anorexia nervosa.

Aim:  Anorexia nervosa is a complex psychiatric disorder posing a rapidly increasing burden on modern societies. Our purpose was to clarify perceptual‐motivational aspects of gustatory disturbances in the disease.

Taste reactivity alterations after IL-1β microinjection into the ventromedial hypothalamic nucleus of the rat

The ventromedial hypothalamic nucleus (VMH) is a central site of action of interleukin-1beta (IL-1beta) induced feeding disturbances. This study was designed to elucidate taste-related perceptual and motivational processes potentially contributing to the anorexia and adipsia seen after bilateral IL-1beta microinjection into the VMH. A saccharin conditioned taste aversion (CTA) paradigm was tested after the central IL-1beta administration. To further investigate whether gustatory deficits are involved in development of the feeding alterations, IL-1beta induced changes of taste responsiveness were also studied in taste reactivity tests. Administration of the cytokine into the VMH did not cause the development of CTA. During taste reactivity tests, however, IL-1beta treated rats displayed significantly poorer ingestive reactions to pleasant taste stimuli than did animals of the control group. In addition, the aversive responses of IL-1beta injected rats to pleasant tastes were significantly more robust than those of control animals. The cytokine treated animals also showed stronger aversion than ingestion to hedonically positive tastes. The present findings indicate that (1) anorexigenic and adipsogenic consequences of IL-1beta microinjection into the VMH are not due to development of cytokine induced CTA; and (2) hedonic responsiveness to palatable tastes is processed by IL-1beta mediated neural mechanisms in the VMH.