is quite complex. They are strongly involved in movement and motor control.
They do NOT initiate movements but they are involved in a loop of modulation with the cortex that is constantly active.
Therefore they are actively involved in monitoring the force to be applied to a task and gross postural adjustments
Main neurotransmitters of Basal ganglia are
GABA, Dopamina and Glutamate
Forebrain - Basal Ganglia 3: Malfunctions
Malfunction or lesion of the basal ganglia:
Parkinson Disease (rhytmical tremor at rest, bradykinesia, muscles rigidity, difficulty in stopping walking once started; difficulty in motor coordination falls)
Reduction of dopamina is mainly due to death of dopaminergic neurons in the substantia nigra. This causes a lack of input (through nigrostriatal path) to putamen
then internal palllidus more activated
then thalamus more hinibeted less activation towards the cortexwhich turns in less movement.
Huntington’s Chorea (jerks, muscle tone poor, possible change in personality, dementia)
Degeneration of striatum
Reduction of GABA neurons and increment of external pallidus activity
which strongly inhibits subthalamic n.then less inhibition of the thalamus more motor activity - involuntary movements)
Ballismus or hemiballismus
(severe involuntary movements of limbs) Lesion of the subthalamic nucleus
Why involuntary movements?
In both Huntington’s Chorea and Ballismus syndromes, the involuntary movements are caused by a abnormal discharges of upper motor neurons that are not adequately inhibited (modulated) by basal ganglia.
Forebrain - Basal Ganglia 4: relationship with cor
Cerebral cortical areas (motor, association, or limbic cortex) project in a topographically arranged manner to basal ganglia.
Sensorimotor and parietal cortices dorsal and mid-sectors of the putamen
Association areas in prefrontal, posterior parietal and superior temporal cortices caudate
Orbital and medial prefrontal cortices and cingulate gyrus ventral nuclei of putamen and caudate
Behavioural-cognitive syndromes (Schmahmann & Pandya, 2008)
Lesions of the:
A) rostral head of caudate impairment of working memory, strategy, formation, flexibility, neglect if right caudate or aphasia if left caudate
B) ventral striatum Behavioural disorders (e.g. disinhibition, irritability, obsessive compulsive disorder)
Forebrain - Thalamus (in Diencephalo) 1
The thalamus has a key role in transforming information to and from the cortex.
It is a large two-lobed structure.
The m***a intermedia is a sort of bridge that connects the two lobes.
The internal medullary lamina divides the medial from the lateral group of nuclei.
External medullary lamina forms the lateral boundary of the thalamus medial to the internal capsule, which contains afferent and efferent nerve fibres p***ing to and from the thalamus to the cerebral cortex
Thalamic nuclei are divided into:
Medial, Lateral and Anterior nuclei
plus the intralaminar nuclei
Each specific nucleus receives connection from the region of the cerebral cortex upon which it projects (usually primary motor and sensory areas)
Receive input from several areas and each nucleus projects to one of the three ***ociation cortex (P-T-O ***. c.; PreF c.; Limbic c.)
Widespread connections also towards other thalamic nuclei and some of these are inhibitory (e.g. reticular formation)
Forebrain - Thalamus 2
Thalamo-cortical projections run through the internal capsule. In the internal capsule there are also the fibers from cortex to
medulla and spinal cord.
The internal capsule continues more laterally and superiorly with the corona radiata, which contains descending axons of the corticospinal tract.
Forebrain - Hypothalamus
The Hypothalamus is a complex structure containing many nuclei and tracts.
It controls the autonomic nervous system and the endocrine system with direct link to the pituitary gland.
- Much of the endocrine system is controlled by hormones produced by cells in the hypothalamus. These hormones (realising – e.g. gonadotropin- releasing hormone) “instruct” the pituitary gland to secrete the specific hormone (e.g.