Basal ganglia

Whilst dysfunction of basal ganglia-thalamic circuitry is implicated in the genesis of parkinsonian symptomatology, few studies have examined the effects of lesioning the motor thalamus in the context of parkinsonism. Forty rats were therefore subdivided into four lesion groups each of 10 rats with lesions or sham surgery targeting (1) the medial forebrain bundle and/or (2) motor thalamus, resulting in: Sham/Sham, 6-OHDA/Sham, Sham/NMDA and 6-OHDA/NMDA groups. Behavioural testing was performed prior to any surgery and after each surgery including analysis of posture, drug-induced rotation, sensorimotor and autonomic deficits. As expected 6-OHDA lesions induced abnormalities in posture, locomotion, sensorimotor and pilomotor function, ipsilateral and contralateral rotational asymmetries after amphetamine and apomorphine, respectively. These behavioural changes reflect parkinsonism in this model. Additional thalamic lesions virtually abolished apomorphine-induced rotational asymmetry and improved sensorimotor response latency to tactile stimulation on the contralateral side. These data support the contribution of dysfunctional motor thalamic circuitry in rotational asymmetry and abnormal sensorimotor function in parkinsonian rats.

The neurochemical organization of the posterior caudate nucleus (CN) (body, gyrus and tail) and putamen (Put) was analyzed in the human brain using adjacent sections stained for acetylcholinesterase (AChE), limbic system-associated membrane protein (LAMP), enkephalin (ENK), parvalbumin (PV), calbindin (CB) and tyrosine hydroxylase (TH). Striosomes were visualized in all striatal regions but the anterior two thirds of the CN tail. They were highly immunoreactive (-ir) for ENK and LAMP, devoid of PV and AChE staining, and surrounded by a ring of tissue with pale TH- and CB-ir neuropil. In the Put, other rings of tissue completely free of ENK labeling surrounded certain striosomes (clear septa). In the CN body, gyrus and tail some markers revealed gradients and heterogeneities along the dorsoventral and mediolateral axes. A rim of striatal tissue densely stained for ENK and LAMP and poorly labeled for PV was noticeable along the lateral edge of the Put and the dorsolateral sector of the CN body. Our results illustrate a chemical architecture in the posterior striatum that is heterogeneous and slightly different from that found in the more anterior striatum.

The superior capability of cognitive experts largely depends on quick automatic processes. To reveal their neural bases, we used functional magnetic resonance imaging to study brain activity of professional and amateur players in a board game named shogi. We found two activations specific to professionals: one in the precuneus of the parietal lobe during perception of board patterns, and the other in the caudate nucleus of the basal ganglia during quick generation of the best next move. Activities at these two sites covaried in relevant tasks. These results suggest that the precuneus-caudate circuit implements the automatic, yet complicated, processes of board-pattern perception and next-move generation in board game experts.

The lamprey belongs to the phylogenetically oldest group of vertebrates that diverged from the mammalian evolutionary line 560 million years ago. A comparison between the lamprey and mammalian basal ganglia establishes a detailed similarity regarding its input from cortex/pallium and thalamus, as well as its intrinsic organisation and projections of the output nuclei. This means that the basal ganglia circuits now present in rodents and primates most likely had evolved already at the dawn of vertebrate evolution. This includes the 'direct pathway' with striatal projection neurons (SPNs) expressing dopamine D1 receptors, which act to inhibit the tonically active GABAergic output neurons in globus pallidus interna and substantia nigra pars reticulata that at rest keep the brainstem motor centres under tonic inhibition. The 'indirect pathway' with dopamine D2 receptor-expressing SPNs and intrinsic basal ganglia nuclei is also conserved. The net effect of the direct path...

The prefrontal cortex (PFC) subserves reasoning in the service of adaptive behavior. Little is known, however, about the architecture of reasoning processes in the PFC. Using computational modeling and neuroimaging, we show here that the human PFC has two concurrent inferential tracks: (i) one from ventromedial to dorsomedial PFC regions that makes probabilistic inferences about the reliability of the ongoing behavioral strategy and arbitrates between adjusting this strategy versus exploring new ones from long-term memory, and (ii) another from polar to lateral PFC regions that makes probabilistic inferences about the reliability of two or three alternative strategies and arbitrates between exploring new strategies versus exploiting these alternative ones. The two tracks interact and, along with the striatum, realize hypothesis testing for accepting versus rejecting newly created strategies.

A sensitive immunofluorescene technique was used to describe systematically the distribution of dopamine-β-hydroxylase (DBH)-containing cell bodies, non-terminal fiber pathways, and terminal fields in the brain of the male albino rat. DBH is the enzyme that catalyzes the conversion of dopamine to noradrenaline, and as such is useful as an anatomical marker for noradrenaline and possibly adrenaline neurons. The enzyme is not present in dopamine- or indolamine-containing neurons. Ten micron frozen sections (1-in-20 series) were prepared in the frontal, sagittal, and horizontal planes from the olfactory bulb to the upper cervical segments of the spinal cord; adjacent sections in each plane were stained for DBH and for cells (toluidine blue-azure II). An atlas consisting of 40 projection drawings of selected frontal sections illustrates the results of the investigation. DBH perikarya are confined to three groups in the pons and medulla: the well defined locus coeruleus, a more diffuse but continuous subcoeruleus group that arches through the pons and ventral medulla, and a third dorsal medullary group centered in the dorsal motor nucleus of the vagus. A single principal adrenergic fiber system distributes a great many of the axons from these neuron groups to a majority of nuclear areas in the brain. In the pons and medulla two components of the fiber system may be distinguished. A medullary branch may be followed from the posterior aspect of the subcoeruleus group dorsally and then anteriorly through the lateral tegmental field and ventral aspect of the vestibular complex to a position subjacent to the locus coeruleus, where it is joined by a subcoeruleus branch consisting of a large number of fibers coursing among cells along the length of the subcoeruleus group, and by fibers arising from the locus coeruleus. Anterior to the locus coeruleus the principal adrenergic bundle courses as a single fiber tract immediately ventrolateral to the central gray in the mesencephalon and in the zona incerta and substantia innominata in the diencephalon. At the level of the septal area separate bundles reach the cortex dorsally over the genu of the corpus callosum via the medial septal-diagonal band nuclei and the lateral septum and ventrally between the olfactory tubercle and caudate-putamen. In the medulla and pons adrenergic fibers undoubtedly course in both directions. Anterior to the most rostral pontine cell bodies, however, all fibers presumably ascend. Along the course of the bundle distinct branches emerge to innervate circumscribed terminal fields. In addition, certain regions of the brain such as the reticular formation and pontine gray receive diffuse DBH innervation derived from less clearly defined pathways. A small number of areas in the brain contain little or no detectable DBH. These include the caudate-putamen, nucleus accumbens, globus pallidus, olfactory tubercle, subthalamic nucleus, substantia nigra, pretectal area, third, fourth and sixth cranial nerve nuclei, and the trapezoid body nucleus.

This article provides current information relevant to school social workers who serve students with obsessive-compulsive disorder (OCD), including how OCD is defined in children and adolescents, the impact of OCD on schooling, issues in identifying students with OCD, and effective interventions. The authors offer suggestions for collaboration among school personnel and families and for linking school with home. Finally, they present recommendations for educating peers of students with OCD.(Contains 2 tables.)

In this study we examined the effect of dopaminergic modulation on learning and memory. Parkinson’s patients were tested on vs. off dopaminergic medication, using a two-phase learning and transfer task. We found that dopaminergic medication was associated with impaired learning of an incrementally acquired concurrent discrimination task, while patients withdrawn from dopaminergic medication performed as well as controls. In addition, we found a dissociation of the effect of dopamine within a single two-phase task: patients tested on medication were not impaired at the ability to generalize based on learned information. The deficit among medicated patients appeared to be related specifically to the concurrent, incremental, feedback-based nature of the task: such a deficit was not found in a version of the task in which demands for concurrent error-processing learning were reduced. Taken together with a growing body of evidence emphasizing a role for midbrain dopamine in error-correct...

Despite the widespread abuse of marijuana, knowledge about its effects in the human brain is limited. Brain glucose metabolism with and without Δ 9 tetrahydrocannabinol (THC) (main psychoactive component of marijuana) was evaluated in eight normal subjects and eight ...