n areas)
There is some correspondence between areas defined by cytoarchitectonic method and their function.
Forebrain - Neocortex 3: Fibres
Associative fibres, which connect areas within the same hemisphere:
Superior and inferior longitudinal fasciculi Cinguale fasciculus
Superior and inferior occipital frontal fasciculus
Commissural fibres, which connect same areas in the two hemispheres:
Fibres of projections, which send (efferent) receive (afferent) information between cortex and other structures of the brain
(e.g. mainly thalamus through internal capsula)
Forebrain - Neocortex 4: Primary Sensory and Motor
Primary Sensory and Motor areas mediate elementary sensory or motor functions
Primary somatosensory area
Associative areas Further process of information
Forebrain - Issues
A few important issues about cortical and subcortical areas: (Schmahmann & Pandya, 2008)
- Lesions in basal ganglia and thalamus mimic deficits resulting from cortical lesions
Due to disruption of the interaction of domain-specific subcortical nuclei with the sensorimotor, association cortical areas.
- However there are qualitative differences between the manifestations of lesions in functionally related area of cortical and subcortical areas
Lesion of primary motor cortex hemiparesis
Lesion of putamen slowness in movements
Lesion of thalamus (VL) ataxia
Lesion of cerebellum lack of motor coordination
Subcortcial areas are topographically arranged
Multiple parallel loops between cortical and subcortical areas with no cross-modal communication within subcortical nuclei
Complex behaviour required interaction between different functional domains Cortex in particular associative areas
Forebrain - Basal Ganglia (in Telencephalo) 1
Basal ganglia are a group of subcortical structures.
The main structure are:
Forebrain - Basal Ganglia 2: Function
Basal ganglia receive direct input from cortical areas and limbic system however
They DO NOT project DIRECTLY to the cortex; Cortical projections travel trough the thalamus
The function of basal ganglia 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 & Pand