Basal Ganglia Synapses, Thalamus & Limbic System

Direct Pathway Synapse 1

Presynaptic: excitatory (Glutamate)

Postsynaptic: inhibitory (GABA)
Outcome: net increase in inhibition

Direct Pathway Synapse 1 Location

From cortex, in striatum

Direct Pathway Synapse 2

Presynaptic: Inhibitory (GABA)

Postsynaptic: inhibitory (GABA)
Outcome: Net decrease in inhibition

Direct Pathway Synapse 2 Location

From striatum, in GPi

Direct Pathway Synapse 3

Presynaptic: Weak Inhibitory (GABA)

Postsynaptic: excitatory
Outcome: Net excitation, to M1 to execute movement

Direct Pathway Synapse 3 Location

From GPi, in thalamus

Indirect Pathway Synapse 1

Presynaptic: Excitatory (Glutamate)

Postsynaptic: inhibitory (GABA)
Outcome: Net increase in inhibition

Indirect Pathway Synapse 1 Location

from cortex, in striatum

Indirect Pathway Synapse 2

Presynaptic: inhibitory (GABA)

Postsynaptic: inhibitory (GABA)
Outcome: Net decrease in inhibition

Indirect Pathway Synapse 2 Location

from striatum, in GPe

Indirect Pathway Synapse 3

Presynaptic: weak inhibitory (GABA)

Postsynaptic: excitatory (Glutamate)
Outcome: Net increase in excitation

Indirect Pathway Synapse 3 Location

from GPe, in STN

Indirect Pathway Synapse 4

Presynaptic: excitatory (Glutamate)

Postsynaptic: inhibitory (GABA)
Outcome: Net increase in inhibition

Indirect Pathway Synapse 4 Location

from STN, in GPi

Indirect Pathway Synapse 5

Presynaptic: inhibitory (GABA)

Postsynaptic: excitatory (Glutamate)
Outcome: Net decrease in excitation, to M1 to inhibit unwanted movements

Indirect Pathway Synapse 5 Location

from GPi, in thalamus

Thalamus function

sensorimotor relay for all senses except olfaction, regulates consciousness & alertness, sleep, and wakefulness

Thalamus Function w/Limbic System

connected to hippocampus to aid with learning and episodic memory

Anterior Nuclei Function

learning, memory, emotion

Ventral posteromedial nuclei function

relay somatosensory inputs from face to S1 and gustation inputs to gustation cortex

Ventral Posterolateral Nuclei Function

relay somatosensory inputs from the body to S1

Dorsomedial Nuclei Function

emotion, cognition, learning

Pulvinar Function

visual and auditory sensation, orientation towards stimulus

Medial Geniculate Body Function

Relay auditory input to auditory cortex in temporal lobe

Lateral Geniculate Body Function

Relay visual input to primary visual cortex

Midline/Intralaminar Nuclei Function

part of RAS, controls arousal, motivation, emotions, and pain

Ventral Anterior Nucleus Inputs

basal ganglia

Ventral Anterior Nucleus Output

M1, premotor, and supplementary motor cortices

Ventral Anterior Nucleus Function

relay basal ganglia inputs to motor cortices for motor planning

Ventral Lateral Nucleus Input

Cerebellum

Ventral Lateral Nucleus Outputs

M1, premotor, and supplementary motor cortices

Ventral Lateral Nucleus Function

relays cerebellar inputs to motor cortices for motor planning and control

Limbic system function

higher order function for emotion, memory, learning, motivation, and social processing

Hypothalamus function

coordinates endocrine system, regulates temperature, autonomics, and appetite

Hypothalamus Input

from various brain regions

Hypothalamus Output

to pituitary then thyroid, adrenal, and reproductive organs

Hippocampus function

essential for memory processing, short term holding and long term transfer

Hippocampus Inputs

from all sensations - olfactory, visual, auditory, and somatosensory

Hippocampus Output

to thalamus, hypothalamus, and limbic structures

Hypothalamus Location

intermediate to pituitary and thalamus

Hippocampus Location

inferior to lateral ventricles

Amygdala Function

regulate anxiety, aggression, fear, emotional memory, and reward pathways

Amygdala Location

anterior border of hippocampus, functionally connects to basal ganglia

Parahippocampal Gyrus function

memory encoding and retrieval of environmental scenes and paralinguistic communication

Parahippocampal Gyrus Location

beside, alongside hippocampus

Entorhinal Cortex Location

rostal portion of parahippocampal gyrus, not structurally separate

Entorhinal Cortex Input

from hippocampus

Entorhinal Cortex Output

to dentate and hippocampus

Entorhinal Cortex Function

hub for spatial memory, navigation, and perception of time