anatomical divisions of the brain

Rostrum (anterior)

‘Towards the beak’

Caudal (posterior)

‘Towards the tail’

Dorsal (superior)

‘Towards the back’

Ventral (inferior)

‘Toward the belly’

Lateral

Toward the side

Medial

Toward the middle

Ipsilateral

On same side of midline

Contralateral

On opposite side of midline

Corpus callosum

Allows communication between two hemispheres - consists of large bundle of axons that connect two hemispheres.

Green and blue (in diagram) represents contralateral connections. Homotopic connects complementary region of other hemisphere. Heterotrophs communicates to a different brain regions. Ipsilateral is on the same side.

Callosotomy

Procedure to cut the corpus collosum to stop severe epileptic seizures - prevents communication between hemispheres

Anatomical subdivisions of the brain

Major divisions - forebrain; midbrain; hindbrain

Subdivision - telencephalon; diencephalon; mesecephalon; metencephalon; myelencephalon

Structures - cerebral cortex; basal ganglia; limbic system; thalamus; hypothalamus; texture/tegmentum; cerebellum; pons; medulla oblongata

Telencephalon - cerebral cortex

Telencephalon is a subdivision of the forebrain & consists of the limbic system, Basal Ganglia and Cerebral Cortex

Cerebral cortex - largest structure of human brain

Divided into two cerebral hemispheres

Inner “white matter” is pale because it has a high proportion of axon fibers covered in fatty myelin layer

Outer “grey matter” where the neurons synapse and connect together

Telencephalon - Basal ganglia

The nuclei of the basal ganglia are responsible for controlling involuntary movement, particular aspects that are highly automatised or involuntary (such as walking)

The basal ganglia are dysfunctional in patients with Parkinson’s disease which leads to weakness, tremors, limb rigidity, poor balance and difficulty initiating movements

Limbic system

Includes hypothalamus, thalamus, cingulate gyrus, fornix, hippocampus, amygdala & orbitofrontal cortex and some nuclei of the basal ganglia and was previously thought to be the emotion circuit.

While the amygdala plays a crucial role in emotions, it is now known the hippocampus & parts of surrounding cortex are involved in learning and memory

Diencephalon - thalamus and hypothalamus

Thalamus - major relay station for sensory inputs to cerebral cortex; divided into several nuclei

Hypothalamus - controls autonomic nervous system and endocrine (hormone) system; regulates survival behaviours (fighting, feeding, fleeing, mating)

Midbrain - Mesencephalon

The midbrain (and hindbrain) are located within the brain stem.

The midbrain (or mesencephalon) is at topmost region of brain stem and sits directly above the hindbrain.

It connects the pons and cerebellum with the forebrain

Plays an important role in motor movement particularly movement of the eye, and in auditory and visual processing

Hindbrain - Metencephalon

Includes the cerebellum (‘little brain’) which receives information from visual, auditory, somatosensory & vestibular (balance) systems helps coordination of movement. Damage to the cerebellum causes problems with walking and leads to jerky poorly coordinated movements and problems maintaining balance.

The pons lies on the ventral surface of the brain stem. It contains several nuclei important tin regulating sleep and arousal; it also relays information from the cerebral cortex to the cerebellum.

Hindbrain - Myelencephalon

The myelencephalon is more commonly called the Medulla oblongata (or Medulla) and links the hindbrain to the spinal cord and contains neurons important for autonomic functions like respiration and hear rate.

Summary of ‘navigating neural space’

• navigational terms allow brain locations ot be described with a common language

• The brain itself is divided into division (forebrain, midbrain and hindbrain)

• These division are further divided into subdivision that includes multiple structures that serve different important functions from motor control to emotion

Primary visual cortex

Occupies medial and lateral parts of the occipital cortex/lobe at the back/posterior of the brain

Receives sensory information from retina

The left and right visual field are each projected to the contralateral hemisphere

Light stimulus from the external environment from both visual fields stimulate the corresponding area of the retina within each eye

Different regions of the retina are represented by different areas within the primary visual cortex

Areas further out in peripheral vision are processed by areas of the visual cortex that extend into the calcarine fissure

Within the primary visual cortex neurons show “orientation selectivity”

Huber and Wiesel won the Nobel prize in 1981 for this work.

Parietal Lobe/Parietal Cortex

Involved in attenuation and spatial awareness

Shots on the dorsal surface of the cortex and is referred to as part of the dorsal stream and the “where” pathway - named for its role in spatial localization

Temporal Lobe/Temperol Cortex

Important in auditory processing

Also involved in more complex visual processing (faces and complex object recognition)

Sits on the ventral surface of the cortex and is part of the ventral stream and the “what” pathway - named for its role in complex object recognition

Primary auditory complex

Occupies superior part of the temporal cortex, as well as a patch of cortex that is buried within the Sylvia’s fissure. It’s receives auditory sensory information from the cochlear (part of the inner ear concerned with hearing)

Primary somatosensory cortex

Located immediately posterior to the central sulcus (large grove between the frontal & parietal lobe)

Receives sensory information from the skin (temperature, touch and pain)

Different regions of skin surface represented by different areas along the strip of cortex, forming a somatotopic map (face & hands over represented)

Primary motor cortex

Located on the precentral gyrus immediately anterior to central sulcus

Different parts of primary motor cortex send signals that control different groups of voluntary muscles (eg hands, feet, lips)

Like the primary sensory cortices, the primary motor cortex controls muscles on the opposite (contralateral) side of the body

Frontal lobe

Human frontal cortex is different from other animals

• relatively larger than non primates

• A higher level of connectivity with rest of the brain (compared to other apes)

“Higher order” functions of the frontal lobes

• voluntary, controlled behaviour

• Impulse control and emotional regulation

• Abstract reasoning and planning

• Social cognition

• Language

Phineas Gage - Classic case of altered “executive functioning” with frontal lobe damage

Railway foreman in Cavendish, Virginia accident involved ‘tamping iron’ (1848)

Survived profound damage to frontal lobe behavioural changes (no longer Gage)

• personality changed profoundly

• Angry, impatient, obstinate, capricious

• Unable to plan for the future

• Not employable in old job (only held jobs where he did not make decisions)

Summary of ‘Lobes of the cerebral cortex’

• understand the key functional divisions of the cortex

  • Lobes of the cerebral cortex

  • Primary visual and auditory cortex

  • Primary somatosensory cortex

  • Primary motor cortex

• Frontal lobe support “higher order” / “executive function”

• The somatosensory and motor cortex work together to process somatosensory information and guide motor action