Parahippocampal Gyrus (Areas 28, 34, 35, 36)

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Parahippocampal Gyrus (Areas 28, 34, 35, 36)

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Location and Boundaries

Location

• Areas 28, 34, 35, and 36: Parahippocampal gyrus, extending lateral and posterior from hippocampus

Area 28 (ventral entorhinal) and area 34 (dorsal entorhinal): Adjacent to hippocampal subiculum

Area 35 (perirhinal cortex) and area 36 (ectorhinal, parahippocampal cortex): Occupy lateral parahippocampal and anterior fusiform gyri

Boundaries

• Entorhinal cortex (areas 28, 34): Comprises anteromedial parahippocampal gyrus

Separated from hippocampus by hippocampal fissure

Boundary with subiculum at medial margin ventral to hippocampal fissure

Separated from perirhinal cortex by collateral sulcus

Areas 28 and 34 separated by tentorial notch

Posteriorly contiguous with retrosplenial cingulate
• Perirhinal cortex (area 35): Immediately lateral to entorhinal cortex

Includes medial bank of collateral sulcus

Bordered by temporal pole (area 38) rostrally

– Anterior margin 2-3 mm anterior to limen insulae at anterior margin of collateral sulcus (~ 24 mm caudal to temporal pole)
• Ectorhinal cortex (area 36): Caudal to perirhinal cortex

Overlapping terms: Ectorhinal, postrhinal, parahippocampal cortex

Includes anterior medial fusiform gyrus

Lateral margin at occipitotemporal sulcus, separating perirhinal from inferior temporal cortex (area 20)

Bordered by fusiform gyrus (area 37) caudally

Function

Spatial Navigation

• Map of spatial location and trajectory in entorhinal cortex with grid cells encoding spatial location and path cells encoding direction

Olfaction

• Primary olfactory cortex located at anterior margin of entorhinal cortex at level of anterior margin of amygdala

Encoding Visual Scenes

• Parahippocampal place area (PPA) in posterior collateral sulcus active during perception of scenes

Memory

• Bridge between hippocampus and neocortex for memory encoding and retrieval
• 2 parallel streams converge on hippocampus

Visual memory: Posterior parahippocampal to medial entorhinal

Nonvisual memory: Perirhinal to lateral entorhinal

Structural Connections

Entorhinal Cortex

• Hippocampus, amygdala, perirhinal, prefrontal cortex, retrosplenial cingulate cortex (areas 29 and 30)

Perirhinal/Ectorhinal Cortex

• Amygdala, basal ganglia, olfactory, prefrontal cortex, sensory association, orbitofrontal cortex (area 11)

Functional Connections

Coactive Regions

• Perirhinal/entorhinal: Middle and inferior temporal cortex (areas 20 and 21), temporal pole (area 38), head of hippocampus
• Posterior parahippocampal: Posterior cingulate cortex (areas 23 and 31), medial prefrontal cortex, inferior parietal lobule (areas 39 and 40), body of hippocampus

Associated Literature Keywords (NeuroSynth)

• Autobiographical, concepts, memories, engaged, recall, sensation, epilepsy, remember, resting state, drugs, difficulty, knowledge

Area 28, 34-to 36-Associated Disorders

Alzheimer Dementia

• Entorhinal cortex shows greatest atrophy, site of earliest pathologic changes

Epilepsy (Medial Temporal Sclerosis)

• Variable involvement of hippocampus, amygdala, and entorhinal/perirhinal cortex

Image Gallery

Print Images

PARAHIPPOCAMPAL GYRUS: LOCATION AND COACTIVATION

Coronal and sagittal slices from a cytoarchitectonic map of the parahippocampal gyrus is shown. This quantitative probabilistic map was derived from postmortem human brains and is specific to cellular properties unique to areas 28, 34, 35, and 36 (data source: SPM Anatomy toolbox).

Coactivation map of Brodmann areas 28, 34, 35, and 36 shows brain regions that reliably activate with the centroid of voxels lying within areas 28, 34, 35, and 36 in over 4,000 studies from the NeuroSynth database. This image is the average of left and right coactivation maps.

CONNECTIVITY TO BILATERAL AREA 36

Functional connectivity MR was averaged from 1,003 typically developing volunteers from the Human Connectome Project dataset. Slices show the correlation to a seed region in the bilateral Brodmann area 36 as defined by the WFU PickAtlas toolbox for MATLAB.

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Tags: Imaging Anatomy Brain and Spine

Mar 13, 2021 | Posted by admin in NUCLEAR MEDICINE | Comments Off

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