Four Lobes of the Cerebral Cortex

Four Lobes of the Cerebral Cortex Structure and function: different parts of the brain control different functions.The frontal Lobe

The frontal LobePrimary motor cortex movement Brocas area speech productionForward area association judging planning initiativeExpression of characteristics associated with personality and emotional behaviour (The motor is in the front of the car Broca is driving)

The frontal Lobe as a car?Phineas gage frontal lobe damageSeptember 13, 1848, 25-year-old Railway foremanPacking gun powder into a hole with a steel pole to blow up rockSparks from the pole ignite the gun powder and send the pole under gages cheek and out the top of his head

Before the accident he was well liked, organised, calm and polite

Phineas gage frontal lobe damageAfter the accident Phineas suffered severe personality changesBecame impulsive, aggressive, disorganised Could not continue his work as foremanAppeared for a time at Barnum's American Museum in New York February 1860, Gage had the first in a series of increasingly severe convulsionsdied in or near San Francisco on May 21 just under twelve years after his accident

Gages case along with others suggest the frontal lobes important role in emotion and personality, planning and initiative

The Parietal lobe

The Parietal lobePrimary Somatosensory cortexReceives info from sensesSomatosensory cortex at front of temporal lobe next to primary motor cortex which is at the back of the frontal lobe

(The party lobe, your senses are going wild at a party)

The Parietal lobe on fire at a party?

Motor and Sensory Cortex organisation

The homunculus man

The temporal Lobe

The temporal LobePrimary auditory areaWernickes area speech comprehensionPrimarily associated with hearingAlso important role in memoryDecisions made about which features of environment we will rememberFacial recognition also performed in temporal lobe

(Temporal sounds like tempo, the tempo of the music)

The Primary Auditory CortexResides in each temporal lobeReceives and processes sounds from both earsEach primary auditory cortex has specialised areas of sound and thus play vital roles in the identification of soundsTwo main features of sound: frequency (perceived as pitch) and amplitude or intensity (perceived as loudness).Each primary auditory cortex is also specialised to process different types of sound. Verbal sounds (e.g. words) in the left hemisphere and non-verbal sounds (e.g. Music) processed in the right hemisphere. BUT there is some overlap, this is not exclusive!Temporal Lobe Association AreasLocated in each temporal lobeDifferent association areas appear to be involved in memory (including linking emotions with memory and determining appropriate emotional responses to sensory info and memories)Amnesia (partial or complete loss of memory) often occurs in people with damage to either or both temporal lobes.Receiving, processing and storing of facts (semantic memories) how to do things (procedural memories) and personal experiences such as birthdays or holidays (episodic memories) appear to occur in areas of the temporal lobes.Object identification and facial recognition are also involved, thus perception and memory to make decisions about our environmental features is an important role of the temporal lobe.. However, perception and memory are not exclusive to one area of the brain but involve many interconnected areas.WERNICKES AREALocated towards the rear of the temporal lobeIn left hemisphere only (next to primary auditory cortex) and connected to Brocas area by a bundle of nerves.Has crucial role in comprehension of speech, but is also involved in speech production, more specifically, interpreting the sounds of human speech.

Word is heard, then the auditory sensation is processed by the primary auditory cortex of the left temporal lobe, but the word cannot be understood until the information has been processed by Wernickes area.WERNICKES AREAAlso vital for not just understanding words, but also for locating appropriate words from memory to express intended meanings when we speak or write.

When a word is to be spoken, a representation of it is transmitted to Brocas area in the frontal lobe which co-ordinates the muscles needed to produce the sound of the word and supplies this information to the face area located where the temporal and occipital lobes intersect.

Damage to Wernickes area causes impairment in understanding speech and to speaking.

Read Box 4.5 on page 194

The temporal Lobe as a drummer?Deep within the temporal lobe- the amygdala

Deep within the Temporal lobe the hippocampusMemory formation not memory storage

Damage leaves patient unable to form new long term memories

The hippocampus lives on memory lane

Deep within the temporal lobe- the amygdalaMediation of fear

Seizures involving the amygdala involve intense fearDamage leaves a person unable to learn a fear response through classical conditioning

Involved in remembering the emotional significance of an event

Damage leaves us unable to judge emotional component of facial expressions in others i.e. angry person perceived as calm or even happyThe Occipital Lobe

The Occipital Lobe Primary visual areaVisual cortex located at base of each occipital lobe is the major destination of visual inforamtion from the two eyes.Other areas visual association areas identifying objects etc.

(Occipital sounds like optical, optical relates to vision)

OCCIPITAL LOBELocated at rearmost area of each cerebral hemisphereAlmost exclusively devoted to the sense of visionDamage can produce blindness even if eyes and neural connections to brain are normalSome areas in other 3 lobes also have important visual functionsDivided into many different visual areas - the largest being the primary visual cortex (at the base of the occipital lobe).

OCCIPITAL LOBEInformation arrives at PVC via visual sensory receptors (photoreceptors) on the retina at the back of each eye.

Each hemisphere receives and processes half of visual information. Left half of each eye receives visual sensory information from right half of visual field and sends info to left occipital lobe and vice versa. See Box 4.12 on page 224

Neurons in the PVC and surrounding secondary visual areas specialise in responding to different visual features e.g. Orientation (direction) of a line, edges, shapes (forms), motion and colour. Some neurons respond to one feature only, others to two or more features.OCCIPITAL LOBE ASSOCIATION AREASHave important roles in vision.They interact with PVC to select, organise and integrate visual information.They interact with association areas of other lobes to integrate visual information with other information (e.g. Memory, language, sounds), so that visual information can be organised and interpreted in a meaningful way.E.g. The frontal lobe (together with parietal lobe) is involved in spatial reasoning such as trying to work out whether a specific piece of a jigsaw puzzle will fit into a particular place in the puzzle.The Occipital Lobe as an eye?

THE EYES IN THE BACK OF YOUR HEAD!MAKE A BRAIN BALL!PATHWAYS FROM THE VISUAL CORTEXAreas other than the visual cortex are also involved in processing visual information to enable visual perception.

Research evidence suggests there are 2 major pathways from the visual cortex in the occipital lobe to areas of the temporal and parietal lobes they are the dorsal stream and the ventral stream.Dorsal and ventral streamsDorsal (upper) stream includes areas of the occipital lobe and leads to parietal lobe.Specialises in locating objects or spatial perception (where an object is and relating it to other objects in a scene). the where pathway

Ventral (lower) stream includes areas of the occipital lobe and leads to the temporal lobe.Specialises in object perception and recognition (identifying objects) the what pathway

See Figure 4.29 on page 197CASE STUDIES OF BRAIN DAMAGED PATIENTSCase studies of patients with brain damage to specific areas of the visual cortex provide evidence in support of the differing roles of the ventral and dorsal streams.

Patient D.F. suffered carbon monoxide poisoning at 34 years of age which damaged brain areas involved in the what pathway.

D.F. could no longer recognise the faces of her friends and family, common objects or even a drawing of a square or circle. Her condition was diagnosed as object agnosia (the inability to recognise objects).D.F.D.F. could recognise people by their voices and could usually say what objects placed in her hands were, through memory of voices and past experiences with objects using touch and other senses.

When presented with a drawing of an apple, D.F. cannot identify or redraw it. But if asked to draw an apple, she can do it from memory.

D.F. can use visual information about the size, shape and orientation of objects to control visually guided movements, suggesting her where pathway has not been damaged. E.g. she can walk across a room and step around things without difficulty and can also reach out and shake hands as easily as we all do.D.F.D.F. can reach out and grasp a block, with the exact correct distance between her fingers, but she cannot tell you what she is going to pick up or how big it is.

Her conscious perception of objects is impaired, she has no awareness of taking in any visual information about objects she sees.