Cumulative blood oxygenation-level-dependent signal changes support the ‘time accumulator’ hypothesis

We studied time-related changes in the blood oxygenation-level-dependent signal during a time reproduction task. Nine healthy study participants retained and reproduced stimuli of varying durations in the multi-second range. During the encoding phase of the task, activity in the left dorsolateral prefrontal cortex inversely correlated with the interval duration, while an adjacent region in the dorsolateral prefrontal cortex showed positive correlation with duration in the reproduction phase. Cumulative signal increase during the reproduction phase, as found in the primary motor and supplementary motor areas, may also reflect the time-sensitive behavior. Signal accumulation in the right caudate nucleus is in agreement with presumed role of basal ganglia in time perception. These results support the 'time accumulator' hypothesis.

Modulation of caudate activity by action contingency

Research has increasingly implicated the striatum in the processing of reward-related information in both animals and humans. However, it is unclear whether human striatal activation is driven solely by the hedonic properties of rewards or whether such activation is reliant on other factors, such as anticipation of upcoming reward or performance of an action to earn a reward. We used event-related functional magnetic resonance imaging to investigate hemodynamic responses to monetary rewards and punishments in three experiments that made use of an oddball paradigm. We presented reward and punishment displays randomly in time, following an anticipatory cue, or following a button press response. Robust and differential activation of the caudate nucleus occurred only when a perception of contingency existed between the button press response and the outcome. This finding suggests that the caudate is involved in reinforcement of action potentially leading to reward, rather than in processing reward per se.

Microanatomy of the subependymal arteries of the lateral ventricle

BACKGROUND

Scarce information about the anatomy of the subependymal arteries (SEAs) is present in the scientific literature.

METHODS

Twenty cerebral hemispheres with injected arteries were microdissected, and the magnetic resonance imaging scans of 100 patients with lacunar infarcts were examined.

RESULTS

The SEAs were found to range in diameter from 40 to 490 microm (mean, 149 microm) and in number between 3 and 12 (average, 5.2). Of these, numbers from 1 to 3 originated from the anterior choroidal artery (AChA), between 1 and 10 from the lateral posterior choroidal artery (LPChA), 1 from the medial posterior choroidal artery (MPChA), and 1 from the internal carotid artery. The SEAs most often arose from the choroidal branches (90%) and less frequently from the thalamic (30%), caudate (35%), or thalamocaudate twigs (20%). The SEAs of the AChA supplied the walls of the temporal horn (100%), the occipital horn (85%), and the atrium (35%). Those of the LPChA perfused the walls of the occipital horn (15%), the atrium (65%), the body of the ventricle (100%), and partially the frontal horn. The SEAs of the MPChA partially nourished the body and the frontal horn (10%). The SEAs may also occasionally supply the caudate nucleus (20%) and the stria terminalis. The anastomoses involving the SEAs were absent. In spite of this, ischemia in the territory of a single SEA was noticed in only 1% of our patients.

CONCLUSIONS

The SEAs are tiny vessels that supply the walls of the lateral ventricle, as well as the caudate nucleus and the stria terminalis occasionally. The obtained anatomic data can have important neurosurgical implications in intraventricular operations.

Perfusion abnormality of the caudate nucleus in patients with paroxysmal kinesigenic choreoathetosis

PURPOSE

Previous cerebral blood flow and glucose metabolism studies suggest that the basal ganglia or thalamus is involved in the pathogenesis of paroxysmal kinesigenic choreoathetosis (PKC). However, the underlying cerebral abnormalities in idiopathic PKC have not been elucidated. To localise cerebral perfusion abnormalities in PKC, we performed interictal brain perfusion 99mTc-ethylcysteinate dimer (ECD) single-photon emission computed tomography (SPECT) in PKC patients and in normal controls.

METHODS

Sixteen patients with idiopathic PKC and 18 age- and sex-matched normal controls were included. The patients were de novo diagnosed as having PKC, or had not taken medication for at least 3 months; none of them had structural abnormalities on MRI. Patients had a history of PKC attacks of a duration not exceeding 5 min and starting either on one side or on both sides of the body. These attacks were always induced by a sudden initiation of voluntary movement. PKC attacks were recorded in a hospital after being induced by neurology staff in 13 of the 16 patients. Interictal brain perfusion 99mTc-ECD SPECT was performed in all 16 patients and 18 normal controls. Differences between the cerebral perfusion in the PKC group and the normal control group were tested by statistical parametric mapping. Student's t test was used for inter-group comparisons.

RESULTS

Compared with normal controls, patients with idiopathic PKC showed interictal hypoperfusion in the posterior regions of the bilateral caudate nuclei (false discovery rate-corrected P<0.001 with a small volume correction).

CONCLUSION

This study showed that cerebral perfusion abnormality of bilateral caudate nuclei is present in idiopathic PKC.

Getting to know you: reputation and trust in a two-person economic exchange

Using a multiround version of an economic exchange (trust game), we report that reciprocity expressed by one player strongly predicts future trust expressed by their partner-a behavioral finding mirrored by neural responses in the dorsal striatum. Here, analyses within and between brains revealed two signals-one encoded by response magnitude, and the other by response timing. Response magnitude correlated with the "intention to trust" on the next play of the game, and the peak of these "intention to trust" responses shifted its time of occurrence by 14 seconds as player reputations developed. This temporal transfer resembles a similar shift of reward prediction errors common to reinforcement learning models, but in the context of a social exchange. These data extend previous model-based functional magnetic resonance imaging studies into the social domain and broaden our view of the spectrum of functions implemented by the dorsal striatum.

Getting to Know You: Reputation and Trust in a Two-Person Economic Exchange

Using a multiround version of an economic exchange (trust game), we report that reciprocity expressed by one player strongly predicts future trust expressed by their partner-a behavioral finding mirrored by neural responses in the dorsal striatum. Here, analyses within and between brains revealed two signals-one encoded by response magnitude, and the other by response timing. Response magnitude correlated with the "intention to trust" on the next play of the game, and the peak of these "intention to trust" responses shifted its time of occurrence by 14 seconds as player reputations developed. This temporal transfer resembles a similar shift of reward prediction errors common to reinforcement learning models, but in the context of a social exchange. These data extend previous model-based functional magnetic resonance imaging studies into the social domain and broaden our view of the spectrum of functions implemented by the dorsal striatum.

The roles of the caudate nucleus in human classification learning

The caudate nucleus is commonly active when learning relationships between stimuli and responses or categories. Previous research has not differentiated between the contributions to learning in the caudate and its contributions to executive functions such as feedback processing. We used event-related functional magnetic resonance imaging while participants learned to categorize visual stimuli as predicting "rain" or "sun." In each trial, participants viewed a stimulus, indicated their prediction via a button press, and then received feedback. Conditions were defined on the bases of stimulus-outcome contingency (deterministic, probabilistic, and random) and feedback (negative and positive). A region of interest analysis was used to examine activity in the head of the caudate, body/tail of the caudate, and putamen. Activity associated with successful learning was localized in the body and tail of the caudate and putamen; this activity increased as the stimulus-outcome contingencies were learned. In contrast, activity in the head of the caudate and ventral striatum was associated most strongly with processing feedback and decreased across trials. The left superior frontal gyrus was more active for deterministic than probabilistic stimuli; conversely, extrastriate visual areas were more active for probabilistic than deterministic stimuli. Overall, hippocampal activity was associated with receiving positive feedback but not with correct classification. Successful learning correlated positively with activity in the body and tail of the caudate nucleus and negatively with activity in the hippocampus.

Peri-infarct depolarizations reveal penumbra-like conditions in striatum

Spreading depression-like peri-infarct depolarizations not only characterize but also worsen penumbra conditions in cortical border zones of experimental focal ischemia. We intended to investigate the relevance of ischemic depolarization in subcortical regions of ischemic territories. Calomel electrodes measured DC potentials simultaneously in the lateral and medial portions of the caudate nucleus (CN) of 11 anesthetized cats after permanent occlusion of the middle cerebral artery. Additionally, platinum electrodes measured cerebral blood flow (CBF) in the CN, and laser Doppler probes CBF in the cortex. Depolarizations (negative DC shifts >10 mV) were obtained in 10 of 11 cats. Further differentiation revealed that short-lasting spreading depression-like depolarizations (SDs; 5 of 10 cats: 5.24 +/- 1.22 min total duration; 23.3 +/- 4.2 mV amplitude) were predominantly found in medial and longer depolarizations (LDs; 4 of 10 cats: 64.7 +/- 47.5 min; 25.0 +/- 11.3 mV) in the lateral CN. Terminal depolarizations (TDs; 6 of 10 cats; without repolarization) occurred immediately after occlusion or at later stages, being then accompanied by elevations of intracranial pressure presumably inducing secondary CBF reduction. CBF tended to be lower in regions with TDs (33.3 +/- 29.9% of control) and LDs (37.3 +/- 22.8%) than in regions with SDs (51.5 +/- 48.0%). We conclude that in focal ischemia, transient peri-infarct depolarizations emerge not only in cortical but also in striatal gray matter, thereby demonstrating the existence of subcortical zones of ischemic penumbra. The generation of these ischemic depolarizations is a multifocal process possibly linked to brain swelling and intracranial pressure rise in the later course of focal ischemia, and therefore a relevant correlate of progressively worsening conditions.

[The peculiarities of speech disturbance in patients with arteriovenous malformations of the caudate nucleus and the thalamus]

Clinical and neuropsychological study of 28 patients with arteriovenous malformations (AVM) of the caudate nucleus and 36 patients with AVM of the thalamus has been conducted. After surgical removal of the caudate nucleus, speech disturbances developed in 4 out of 8 patients with left-side AVM and in 1 patient, a converted left-hander, with right-side AVM. All 5 patients had mild speech disturbances, which differed by character in dependence of the AVM location. In case of AVM location in the head of the caudate nucleus, the speech disturbances were represented by perseverations and were similar to those caused by the lesion in the Broca area. In case of the caudate nucleus lesion, naming was mildly affected that resembled temporal aphasia. After surgical removal of AVM in the left thalamus in 9 patients, complex and rather stable speech disturbances developed in 7 cases. They were featured by the signs of frontal and temporal aphasias, i.e. there were perseverations and disturbances of naming, auditory and speech memory. The peculiarities of speech disturbances in lesions of the caudate nucleus and the thalamus were well explained by their anatomic and functional correlations with different regions of brain speech cortex. Speech disturbances in various subcortical lesions are reviewed. In the authors' opinion, subcortical aphasias do not have any particular character but include the same factors in different combinations as cortical ones that is determined by the presence of common functional systems for speech support which comprise cortical and subcortical patterns.

A meta-analysis of functional neuroimaging in obsessive-compulsive disorder

Recent neurobiological models of obsessive-compulsive disorder (OCD) posit that a dysfunction in orbitofrontal-subcortical circuitry underlies the etiology of this disorder. Much of the empirical support for these theories comes from studies using neuroimaging techniques to compare brain activity in OCD patients with that in non-OCD controls. Qualitative reviews of this literature implicate the orbitofrontal cortex, caudate nuclei, and thalamus. In this study, a meta-analysis was conducted to summarize the results of studies using positron emission tomography (PET) and single photon emission computed tomography (SPECT) to investigate brain activity in OCD. Results suggest that differences in radiotracer uptake between patients with OCD and healthy controls have been found consistently in the orbital gyrus and the head of the caudate nucleus. No other significant differences were found. The implications of these results for theories regarding the etiology of OCD are discussed.

Oral methylphenidate challenge selectively decreases putaminal T2 in healthy subjects

Despite the recent rise in oral methylphenidate (MPH) abuse, few studies have characterized the time course of oral MPH brain effects in human subjects. Accordingly, this study assessed the hemodynamic effects of oral MPH effects in 11 healthy young adults (six women), by measuring brain transverse relaxation times (T2). T2 can be interpreted as a surrogate marker for, and inversely correlated with, steady-state cerebral blood volume (CBV). Data were acquired from the caudate nucleus, putamen, and thalamus, using a 1.5 T MRI scanner at baseline and serially for 2 h following oral MPH administration (0.5 mg/kg). Physiological and subjective measures and plasma MPH levels also were examined. MPH induced a selective T2 decrease (-1.65+/-0.53 ms) in the putamen (F(6,54)=2.68, P<0.03). Heartrate, blood pressure and plasma MPH levels increased significantly after drug administration, as well as subjective ratings of "feeling drug effect". T2 decreases may reflect MPH-induced increases in putaminal blood volume. These data suggest that T2 relaxometry can be used to study the time course of regional cerebral blood volume responses to MPH and perhaps to other stimulant drugs.

Atypical MR imaging perfusion in developmental venous anomalies

Developmental venous anomalies (DVAs) are common variants of cerebral venous drainage that are typically incidental findings on contrast-enhanced MR imaging studies. We present four cases of asymptomatic DVAs that demonstrate increased cerebral blood flow, cerebral blood volume, mean transit time, and time to peak on perfusion MR images. Our study indicates that alterations in perfusion MR imaging parameters can be seen with uncomplicated DVAs and do not necessarily imply a more ominous underlying etiologic factor, such as hypervascular tumor or stroke.

Obsessive-compulsive disorder after unilateral caudate nucleus bleeding

Obsessive compulsive disorders (OCD) may be encountered after basal ganglia lesions of various aetiologies. These lesions are usually bilateral. We report here the case of a 24 years old man who developed a pure compulsive behavior after a unilateral left-sided caudate nucleus hemorrhage due to a cavernoma. The pathophysiology of this compulsive disorder probably reflects a frontal cortex deafferentation mechanism. Behavioral, psychological and medical (serotoninergic) treatments are usually proposed but the efficacy of such therapy remains to be investigated in secondary OCD.

Regional cerebral hyperperfusion with ictal dystonic posturing: ictal-interictal SPECT subtraction

PURPOSE

Ictal-interictal single-photon emission computed tomography (SPECT) subtraction was performed to find brain structures related to ictal dystonic posturing (DP) in patients with temporal lobe epilepsy (TLE).

METHODS

Thirty-two patients with mesial TLE who had ictal and interictal SPECTs were included. They were divided into two groups; DP group with ictal dystonia during ictal SPECT (n = 15) and Non-DP group without ictal DP (n = 17). Ictal-interictal SPECT subtraction was performed, and then subtracted SPECT was coregistered with brain spoiled gradient recalled (SPGR) magnetic resonance imaging (MRI). The ictal hyperperfusion on subtracted SPECT was analyzed in basal ganglia, frontal cortex, thalamus, temporal lobe, and insular cortex.

RESULTS

The incidences of ictal hyperperfusion on brain regions in DP versus Non-DP groups were 80.0% (12 of 15 patients) versus none (0 of 17), p = 0.001, chi2, in caudate nucleus; 93.3% (14 of 15) versus 47.0% (eight of 17), p = 0.005, in putamen; and 80.0% (12 of 15) versus 41.2% (seven of 17), p = 0.026, in thalamus. No significant difference of ictal hyperperfusion was found in globus pallidus, temporal lobes, insular and frontal cortices between DP and Non-DP groups. DP patients showed an earlier age at seizure onset [8.6 years (DP) vs. 15.7 years (Non-DP) (p = 0.015)] and a longer duration of seizure history [19.0 years (DP) vs. 11.9 years (Non-DP) (p = 0.015)].

CONCLUSIONS

Caudate nucleus, putamen, and thalamus were significantly related to the ictal DP during TLE seizures. Our study showed first an active involvement of the caudate nucleus in the generation of ictal DP.

Neuroprotection by a selective estrogen receptor beta agonist in a mouse model of global ischemia

The present study employs selective estrogen receptor (ER) agonists to determine whether 17beta-estradiol-induced neuroprotection in global ischemia is receptor mediated and, if so, which subtype of receptor (ERalpha or ERbeta) is predominantly responsible. Halothane-anesthetized female C57Bl/6J mice were ovariectomized, and osmotic minipumps containing ERbeta agonist diarylpropiolnitrile (DPN) (8 mg.kg(-1).day(-1), n = 12) or vehicle (50% DMSO in 0.9% saline) (n = 9) or ERalpha agonist propyl pyrazole triol (PPT) (2 mg.kg(-1).day(-1), n = 13) or vehicle (50% DMSO in 0.9% saline) (n = 10) were implanted subcutaneously. One week later transient global ischemia was induced by bilateral carotid artery occlusion under halothane anesthesia, and the mice were perfusion fixed 72 h later. ERbeta agonist DPN significantly reduced ischemic damage by 70% in the caudate nucleus and 55% in the CA1 region compared with vehicle controls (P < 0.05, Mann-Whitney U-statistic). In contrast, pretreatment with the ERalpha agonist PPT had no effect on the extent of neuronal damage compared with controls. The data indicate a significant estrogen receptor-mediated neuroprotection in a global cerebral ischemia model involving ERbeta.

Normal pressure hydrocephalus and cerebral blood flow: a PET study of baseline values

Regional cerebral blood flow (CBF) was studied with O(15)-water positron emission tomography and anatomic region-of-interest analysis on co-registered magnetic resonance in patients with idiopathic (n = 12) and secondary (n = 5) normal pressure hydrocephalus (NPH). Mean CBF was compared with values obtained from healthy volunteers (n = 12) and with clinical parameters. Mean CBF was significantly decreased in the cerebrum and cerebellum of patients with NPH. The regional analysis demonstrated that CBF was reduced in the basal ganglia and the thalamus but not in white matter regions. The results suggest that the role of the basal ganglia and thalamus in NPH may be more prominent than currently appreciated. The implications for theories regarding the pathogenesis of NPH are discussed.

Brain reactivity to specific symptom provocation indicates prospective therapeutic outcome in OCD

A pertinent question in biological psychiatry is what differentiates responders and non-responders to pharmacological treatment. One possibility is that individual differences in the symptomatic spectrum as well as in the underlying biology of the disorder lead to the known 40% failure in pharmacological treatment. Our study aimed to maximize individual brain markers of obsessive-compulsive disorder (OCD) by applying single photon emission computed tomography (SPECT) during a provoked symptomatic state prior to and following treatment. Four brain SPECT scans were obtained from 26 OCD patients prior to and at 6 months of sertraline treatment. At each time point, two SPECT scans were performed in a counterbalanced order of two specific states; one a symptom-provoking condition and the other a relaxed condition. At 6 months of treatment, patients were divided into responders and non-responders according to a predetermined clinical criterion. Prospective responders showed significantly lower brain perfusion in the dorsal-caudal anterior cingulum and higher brain perfusion in the right caudate, when compared to non-responders, only during symptom provocation. When pre- and post-treatment scans during symptom provocation were compared, only responders showed significant change in brain response: increased perfusion in the left anterior temporal cortex and prefrontal cortex at 6 months' treatment. These findings suggest that obtaining functional brain imaging during specific symptom provocation emphasizes individual differences in brain reactivity. Thus can indicate prospective responders to symptom-related treatment in OCD and mark the relevant brain regions for effective response to treatment.

Positron emission tomography of striatal serotonin transporters in Parkinson disease

BACKGROUND

Little is known about serotonin neurons in Parkinson disease (PD).

OBJECTIVE

To study the serotonin system in PD with positron emission tomography, using the serotonin transporter radioligand [11C](+)McN5652.

DESIGN AND PATIENTS

We measured the density of the serotonin transporter and the density of [11C]WIN35,428-labeled dopamine transporters in the striatum of 13 adults with PD and 13 age- and sex-matched controls. To assess the effects of possible differences in blood flow or brain atrophy, we also measured regional cerebral blood flow and the size of the regions of interest for the caudate nucleus and putamen.

RESULTS

Patients with PD showed reductions in the specific distribution volumes of [11C](+)McN5652 in the caudate (P<.01) and putamen (P<.01), along with the expected reductions in striatal [11C]WIN35,428 binding (P<.01). There were no reductions in regional cerebral blood flow or the sizes of the regions of interest, mitigating against potential confounding effects of blood flow, brain atrophy, or partial volume effects. Reductions in serotonin transporter binding correlated with ratings of disease staging.

CONCLUSIONS

These results suggest that the density of serotonin transporters, like that of dopamine transporters, is reduced in the striatum of patients with PD and that these changes are related to disease stage.

Early-onset anorexia nervosa: is there evidence of limbic system imbalance?

OBJECTIVE

This study, part of a continuing effort to understand the pathophysiology of the brain in early-onset anorexia nervosa, attempts to validate findings from an earlier study of regional cerebral blood flow and to correlate any abnormalities in blood flow with eating disorder psychopathology.

METHOD

Fifteen newly referred children and adolescents with a diagnosis of anorexia nervosa (AN) underwent regional cerebral blood flow (rCBF) examination using single-photon computerized tomography (SPECT) and the Eating Disorders Examination (EDE) for children.

RESULTS

Mean age was 14 years 11 months (SD = 1.35). Mean weight for height ratio was 82.79 % (SD = 10.66). SPECT findings showed that 11 (73%) had asymmetry (hypoperfusion) of blood flow in at least one area. Regions of the brain showing hypoperfusion included the temporal lobe (n = 9), parietal lobe (n = 5), frontal lobe (n = 3), thalamus (n = 3), and the caudate nuclei (n = 1). The median EDE subscale scores were high for all four subscales. Those patients with hypoperfusion had higher median EDE subscale scores than those without hypoperfusion, although the differences were not statistically significant.

CONCLUSIONS

Most patients in our study had abnormal rCBF, predominantly affecting the temporal lobe, confirming our previous findings. There was no association with the EDE scores. The findings support earlier suggestions of an imbalance in neural pathways or circuits, possibly within the limbic system. This hypothesis is considered within the context of current knowledge and suggestions made with regard to how it might be tested.

Nocardiosis with brain abscess due to an unusual species, Nocardia transvalensis

The identification of Nocardia transvalensis, an unusual and probably underrecognized cause of nocardial infection, is clinically significant because of this species' resistance to aminoglycosides, a standard antinocardial therapy. Diagnosis requires analytic methods available predominately in reference laboratories. We report a case of disseminated infection with N transvalensis with primary pulmonary involvement and subsequent development of brain abscesses, and review the literature to date. Familiarity with the epidemiology, pathologic findings, and clinical significance of this and other unusual Nocardia species may increase early identification and antibiotic susceptibility testing in cases of nocardial infection.

Cerebral blood volume and clinical changes on the third day of placebo substitution for SSRI treatment

BACKGROUND

Interruptions in SSRI treatment have been associated with adverse effects that can resemble depressive illness. We hypothesized that brain regions implicated in depression, with extensive serotonergic innervation, would exhibit changes in activity associated with emergence of symptoms following drug discontinuation.

METHODS

Subjects meeting DSM-IV criteria for remitted major depression on 20 mg/day of either fluoxetine or paroxetine were recruited into this 6-week study. During weeks 2 and 6, subjects underwent a 3-day period in which either active drug or placebo was substituted for their medication under double-blind conditions. Cerebral blood volume (CBV) maps were obtained via dynamic susceptibility magnetic resonance imaging at the end of each double-blind period.

RESULTS

In the paroxetine group, change in CBV in left medial superior frontal region and left caudate nucleus correlated significantly with change in Discontinuation Emergent Symptom Scale and Hamilton Depression Rating Scale (HDRS; R2 = 0.66, p =.0007; R2 = 0.51, p =.006; and R2 = 0.43, p =.015; R2 = 0.32, p =.043, respectively).

CONCLUSIONS

These data demonstrate that changes in regional CBV of left prefrontal cortex and left caudate nucleus correlate with the emergence of discontinuation symptoms and increased HDRS after interruption of paroxetine treatment.

The unilateral spatial neglect phenomenon in patients with arteriovenous malformations of deep brain structures

Clinical-neuropsychological investigations were performed in 187 patients with arteriovenous malformations (AVM) of deep brain structures; 28 had AVM of the caudate nucleus, 35 of the thalamus, 45 of the cingulate gyrus, 43 of the hippocampus, and 36 of the corpus callosum. A total of 47 patients displayed neglect phenomena of different modalities, while unfixed neglect was demonstrated in 40 cases using special tests. The vast majority of patients showed neglect of left-sided space and the left side of the body, while only three patients showed right-sided neglect. These three patients had signs of left-handedness. In the development of neglect in all patients was associated with post-hemorrhagic or post-operative damage to the white matter (the projections of sensory bundles of the parietal and occipital lobes, the periventricular white matter) or the thalamus and corpus callosum. In hemispheric lesions, neglect developed on the background of the corresponding derangements (hemihypesthesia hemianopsia) and were of the same modality. In cases of damage to the corpus callosum, neglect could develop without accompanying sensory disturbances or the phenomenon could occur on different sides (in cases of simultaneous left hemisphere damage). This supports the independent nature of the neglect phenomenon.

Differences in the extent of primary ischemic damage between middle cerebral artery coagulation and intraluminal occlusion models

The authors studied the differences between heat-shock/stress protein 70 (hsp70) gene expression and protein synthesis in the unilateral middle cerebral artery (MCA) microsurgical direct occlusion (Tamura's) model and the unilateral intraluminal occlusion model. In Tamura's model, expression of hsp70 mRNA and HSP70 protein and decreased protein synthesis were detected in the ischemic areas, including the ipsilateral cortex and caudate. These phenomena, however, were not observed in the areas outside the MCA territory, including the ipsilateral thalamus, hippocampus, and substantia nigra. These results were consistent among the experimental rats. In the intraluminal occlusion model, however, induction of both hsp70 mRNA and HSP70 protein and impairment of protein synthesis were noted in the areas outside the MCA territory, including the ipsilateral thalamus, hypothalamus, hippocampus, and substantia nigra, as well as in the MCA territory, including the ipsilateral cortex and caudate. These results were not consistent among the experimental rats. These different results might be due to widespread damage resulting from internal carotid artery (ICA) occlusion in the intraluminal occlusion model. Accordingly, the authors suggest that this model be called an ICA occlusion model, rather than a pure MCA occlusion model.

Effect of satiation on brain activity in obese and lean women

OBJECTIVE

To investigate the response of the brains of women to the ingestion of a meal.

RESEARCH METHODS AND PROCEDURES

We used measures of regional cerebral blood flow (rCBF), a marker of neuronal activity, by positron emission tomography to describe the functional anatomy of satiation, i.e., the response to a liquid meal in the context of extreme hunger (36-hour fast) in 10 lean (BMI < or = 25 kg/m(2); 32 +/- 10 years old, 61 +/- 7 kg; mean +/- SD) and 12 obese (BMI > or = 35 kg/m(2); 30 +/- 7 years old, 110 +/- 14 kg) women.

RESULTS

In lean and obese women, satiation produced significant increases in rCBF in the vicinity of the prefrontal cortex (p < 0.005). Satiation also produced significant decreases in rCBF in several regions including the thalamus, insular cortex, parahippocampal gyrus, temporal cortex, and cerebellum (in lean and obese women), and hypothalamus, cingulate, nucleus accumbens, and amygdala (in obese women only; all p < 0.005). Compared with lean women, obese women had significantly greater increases in rCBF in the ventral prefrontal cortex and had significantly greater decreases in the paralimbic areas and in areas of the frontal and temporal cortex.

DISCUSSION

This study indicates that satiation elicits differential brain responses in obese and lean women. It also lends additional support to the hypothesis that the paralimbic areas participate in a central orexigenic network modulated by the prefrontal cortex through feedback loops.