Encoding Pt 1 - Association Cortices

Key terms

• Cortex vs Lobe 

• Sulcus (plural sulci) 

• Gyrus (plural gyri) 

• Brodmann Area 

• White Matter Tracks 

• Laterality 

Sulci and Gyri

Gyri - Grooves

Sulci - Fissures

Central Sulcus

Separates Parietal and Frontal Cortices

Insula (Insular Cortex)

The insula is important for the feeling of disgust

Brodmann Areas

• 'Map' of the cortex 

• First mapped by Korbinian Brodmann in 1909 

• Based upon areas of similarity in histology 

• Still widely used today 

• 52 regions, some subdivided 

Posterior Parietal Cortex – Attending to stimuli 

• Broadmann area 5,7,39,40 

Important for attention  

• Especially spatial attention 

• Integrates visual, auditory and somatosensory info 

• Damage results in 'neglect' 

Neglect

• A sign of posterior Parietal cortex damage

• Sensory neglect – Incoming sensory information from the contralateral hemispace is ignored 

• Conceptual neglect – neglect of the body and the external world in the contralateral hemifield  

• Hemiasomatognosia – patient denies that affected side of body belongs to them 

• Motor neglect – fewer movements in the contralateral space 

Temporal Cortex

Identifying the nature of stimuli (what is it?) 

Agnosia

non-knowledge, or loss of knowledge, is an inability to recognise sensory stimuli and a sign of Temporal Cortex damage 

Inferior Temporal Cortex damage

• Visual agnosia (psychich blindness)  

Patient can see, but no identify 

Fusiform gyrus

• Prosopagnosia (face blindness)

Inability to recognise individuals from their faces. Patients can describe the constituent parts of the face and can identify the subject by voice, clothes and other cues 

Middle Temporal cortex damage

• Movement agnosia 

Cannot distinguish between moving and stationary 

Integration of sensory streams

Allow us to assemble one coherent perspective on the world 

The McGurk effect

• It happens, even when you know its happening 

• In humans, vision is the dominant sense (ish) 

• Large variation in how people experience it 

• Reduced in Dyselxia, Autism 

Integrating audio and visual information in speech processing

Superior Temporal Sulcus

Frontal Cortex – Selecting and planning an appropriate response (What to do about it?) 

Prefrontal cortex 

• Rostral to Primary Motor Cortex 

• Very large in humans 

• Develops very late 20-20 – is why many mental health conditions develop late 

• Dorsal – thoughts, attention 

• Ventral – emotion 

 

• Restraint – Judgement, foresight, inhibiting appropriate actions, concentration 

• Initiative – drive, creativity, curiosity, personality, flexibility 

• Order – planning, abstract reasoning, working memory, attention 

Frontal cortex damage

• Difficulty planning sequence needed to complete a task (e.g., making a cup of tea) - requires working memory 

• Loss of spontaneous interactions  

• Loss of flexibility in thought 

• Perseveration – persistence of a single thought or action 

• Inability to focus on the task in hand 

• Emotional lability  

• Abulia – passivity, apathy 

• Socially inappropriate behaviour 

• Personality change  

• Difficulty with problem solving 

• Expressive aphasia 

• Hemiplegia 

Executive function –resides in the prefrontal cortex 

• Long-term planning 

• Withholding impulsive behaviour 

• 'Cognitive control' 

Important in many pathologies 

• Addiction 

• Personality Disorders 

• Dementia 

Important in everyday behaviours 

White Matter Tracts

Connect the Association Cortices  

Not really visible by physical exam, CT or static MRI 

• Poorly understood 

• Use diffusion tensor imaging to map – tactography, a form of MRI 

Association fibres

• Connect cortical areas in the same hemisphere 

Superior Longitudinal Fasciculus – An example of an Association tract 

Commisural fibres

• Connect across hemispheres 

Corpus Callosum (connect hemispheres) 

An example of a Commisural tract 

Projection fibres

• Connect cortex to other brain regions

Corticospinal (motor) and Corona-radiata - examples of projection tracts

Language

Cortical areas working together

Speech difficulties - How do they arise?

Dysarthria 

• Difficulty moving the muscles of the face + tongue that mediates speaking 

Aphasia 

• Difficulty in naming objects, repetition of words is impaired 

Wernicke’s Area - Understanding language

Wernicke's Aphasia 

• Unable to understand language 

• Fluent speech, but makes no sense (assuming Broca's area intact), little repetition, adequate syntax and grammar, contrived or inappropriate speech 

Which Brodmann Area(s) is Wernicke’s Area located in?

Brodmann Area 22

Which Brodmann Area(s) is the Auditory Cortex located in?

Brodmann 41+ 42

Damage to Wernicke’s Area

• Often as a result of a stroke 

• Also called fluent, sensory or receptive aphasia 

Broca’s Area

Brodmann 44 + 45

Broca’s Aphasia

• Few problems understanding language – assuming Wernicke's area intact 

Difficulty constricting their own 

• Halting speech 

• Repetitive 

• Disordered syntax + grammar 

• Disordered structure of individual words 

• Also called non-fluent, motor, expressive or production aphasia 

Damage to Broca’s Area

• Often as a result of stroke 

• (Different) branches of the Middle Cerebral Artery 

Aphasias

• Recognition of 'conversation cues' seems ok 

• Affects other forms of language: reading, writing, sign language 

• Many other forms of aphasia 

Arcuate Fasciculus

Connects Broca’s + Wernicke’s Areas