Cerebral Function

Brodmann Map

•Developed by Korbinian Brodmann (1868-1918)

•Divides brain into 52 areas based on:

–Brain’s gross anatomy

–Cellular structure of brain

•Areas called Brodmann areas (BA)

Frontal Lobe: Prefrontal Cortex

•Occupies BA 9, 10, 11, 46, 47

•Functionally involved with cognition (executive control), personality, decision making, and social behavior

•19th century case of Phineas Gage and his prefrontal cortex damage taught much re: the functioning of this area

Prefrontal Cortex Damage Chart: 

Frontal Lobe: Frontal Eye Fields

•Occupies BA 8

•Controls eye movements (up, down, left, and right)

•Damage results in eyes deviating toward the side of injury

•Involved in uncertainty and hope

•Sometimes included as part of prefrontal cortex

Frontal Lobe: Premotor Cortex

•Occupies BA 6

•Close relationship to BA 44

•Involved in selecting and planning of motor movements

•Supplementary motor area (SMA) located at top of BA 6 and is involved sequencing and “turning on” motor plans

Frontal Lobe: Primary Motor Cortex

•Occupies BA 4

•Sends motor plans developed in BA 6 to the muscles for them to act (e.g., speech muscles)

•BA 4 has been mapped to form a homunculus or “little man”

Parietal Lobe: Primary Sensory Cortex•

Occupies BA 1, 2, and 3

•Processes somatosensory information such as:

–Vibration

–Proprioception

–Touch

–Stereognosis

•Homunculus present

Parietal Lobe: Somatosensory Association Cortex•Occupies BA 5 and 7

•Interprets sensory experience during motor movements

•This sensory experience is used to refine motor action

•Involved in the fine movements associated with speech

•Plays role in writing sensory & motor experience

Parietal Lobe: Angular Gyrus

•Occupies BA 39

•Involved in reading and math abilities

•Damage can lead to alexia and alcalculia•

May also be involved in understanding metaphors and our sense of embodiment

•Damage can lead to outer body experiences (OBEs)

•Damage can also lead to Gerstmann syndrome

Parietal Lobe: Supramarginal Gyrus•Occupies BA 40

•Closely rated to the angular gyrus (BA 39)

•Involved in phonological system; stores auditory representations of phonemes (auditory images)

•This helps us sound out words

•Damage can result in phonological dyslexia, difficulty reading new and non-words

Occipital Lobe: Visual Cortices

•Occupies BA 17, 18, and 19

•Where information from eyes is received and processed

•Two streams of vision:

–Dorsal stream (18, 19, 7, and 39?): the where of vision; analyzes motion and spatial relationships

–Ventral stream (18, 19, and 37): the what of vision; analyzes forms, colors, and faces

Temporal Lobe: Inferior Temporal Area

•Occupies BA 20 and 21

•Involved in processing of auditory and language information as well as reading facial emotions

•May play a role in hallucinations

Temporal Lobe: Parahippocampal Gyrus

•Occupies BA 27, 28, 34, 35, and 36

•Located on medial surface of temporal lobe

•Two structures of note:

–Hippocampus: associated with declarative memory

–Entorhinal cortex (BA 28 and 34): major input/output relax between the cerebral cortex and the hippocampus

Temporal Lobe: Fusiform Gyrus

•Occupies BA 37

•a.k.a., occipitotemporal gyrus

•Important in remembering and naming seen objects

•Functions as a visual lexicon

•Lesions can cause anomia and lexical agraphia

Temporal Lobe: Primary Olfactory Cortex 

•Occupies BA 38

•Receives and processes olfactory (smell) sensory information from the nose via the olfactory bulbs

•Has connections to the limbic system (emotional processing system), which explains why smells can evoke emotions and emotional memories

•Damage can lead to anosmia, or a loss of smell

Temporal Lobe: Primary Auditory Cortex

•Occupies BA 41 and 42 (42 is the secondary auditory cortex, but 41/42 usually discussed as a unit called the primary auditory cortex)

•a.k.a., Heschl’s gyrus

•Initial cortical region that receives auditory information from the ears via CN VIII and the auditory pathway

•Processes sound intensity and frequency

•Organized by tones (tonographically arranged)

Cingulate Cortex:

•Name means “band that encircles”

•Occupies BA 23-26, 30-33

•Sandwiched between corpus callosum and frontal and parietal lobes

•Is part of the limbic system and has connections to the profronal cortex and hippocampus

•Functionally, involved in the following:

–Anterior parts: cognitive control, detecting errors, detecting conflicts, and problem solving

–Posterior parts: autobiographical memory, managing risky behavior, emotional processing

•Overall, there appears to be a filter and focus process

–ACC filters out irrelevant information

–PCC detecting important information

Insular Cortex:

•Located deep in the lateral sulcus

•a.k.a., insula or island

•Two main parts:

–Posterior-dorsal area: orofacial programs and emotions (e.g., disgust over drinking spoiled milk)

–Dorsal-caudal area: connections to BA 5 and 7, so involved in integrating sensory feedback into motor behavior (e.g., refinement)

•Clinical date suggests role in language

•Perhaps plays role in lexical decision making

•May be involved in some cases of global aphasia