w10 biopscyh - human language

Lateralization

Spatial cognition - RHS

Language LHS. for 90% of population despite if you are left handed or right

RHS speech dominance only in 4% of right handed, 15% in ambidextrous, 27% in left handed.

laterality of brain fully developed after 5 years

Incidence of language problems due to damage ln LHS is much greater before age of 5 yrs.

left hemispherectomy in adults results in aphasia whereas in children almost complete recovery of langauge function.

Broca

Broca = inferior left frontal cortex

Aphasia - slow, laborious and non fluent. Mispronunciation of words - order of sounds wrong. Only use verbs and nouns and misses connecting words

Damage of brain must extend to frontal lobe and underlying subcortical white matter for Broca’s aphasia

Study - had subjects read out verbs that related to body actions. Looked at most active areas of brain. Face words - part of motor cortex lit up. Arm and leg same.

Agrammatism -

Agrammatism

difficulty comprehending or properly employing grammer such as verb endings (ed) and word order. also difficulty producing function words e.g. the, a ,some. Can say content words that convey meaning e.g. apple. E.g. asked to describe pic of boy playing baseball. Became boy is catch.

Problem understanding word order - when had to choose between photos of cow kicking horse and horse kicking cow “horse kicks cow” they couldnt chose correctly as couldnt comprehend word order. Due to frontal lobe being responsible for order

Difficulty following simple commands when word order is important e.g. pick up red circle and touch red square.

Left frontal cortex damage.

Wernickes’ area

Left temporal lobe. In the auditory association cortex. Analyse info received from auditory cortex to give it meaning.

Disruption to recognising spoken words, comprehension of meaning of words, ability to convert thought into words.

pure word deafness (recognition)

Transcortical sensory aphasia (comprehension)

Wernickes aphasia = pure word deafness + TSA.

Conduction aphasia -

Pure word deafness

pure word deafness (recognition) - no recognition of word but comprehension is intact

Ability to hear and speak and read and write without being able to comprehend meaning of speech. Damage to Wernickes or disruption to auditory input to this region

Case study - patients had perfect hearing but couldnt understand spoken commands. Could understand written command

Brain injury to either superior temporal cortex or Wernickes

Transcortical sensory aphasia

- recognition without comprehension. Damage to posterior language area alone which isolates Wernickes from rest of posterior language area.

Difficulty producing meaningful spontaneous speech but can repeat speech.

Conduction aphasia

inability to repeat words that are heard but the ability to speak normally and comprehend speech of others. Can understand words but cant repeat them.

Damage to arcuate fascicular. Connection between wernickes and broca

Suggests there are 2 pathways between wernicks and broca. Direct connection - conveys speech sounds. This would be expected to cause conduction aphasia. Indirect pathway - through posterior language area. Should have ability to repeat speech but impair comprehension. Transcortical sensory aphasia.

Brain structures associated with reading

Primary visual cortex. Occipital

Visual association cortex. Temporal

Visual word form area (VWFA). Bottom temporal

Broca

Pure Alexia / pure word blindness

Loss of ability to read without loss of ability to write. Lesion in visual cortex of left occipital lobe and posterior end of corpus callosum.

Info from left visual field is transmitted to right striate cortex (primary visual cortex) and then to regions of right visual association cortex.

From there info crosses the posterior corpus callosum and is transmitted to a region of the left visual association cortex (VWFA) where it is analysed at goes to Wernickes

The info is then transmitted to speech mechanisms located to the left frontal lobe. This the person can read words aloud

damage to corpus callosum and left visual cortex stop people being able to read words.

Case reported of man with multiple sclerosis who displayed he symptoms of pure alexia after sustaining a lesion that damaged both the subcortical white matter of the left occipital lobe amd thr posterior corpus callosum. Lesions are in precisely the locations that were predicted

Comprehending written words

Reading involves 2 processes

• whole word reading - seeing word as whole

• Phonetic resding - reading by decoding the phonetic significance of letter strings “sound reading”

Surface dyslexia

Surface dyslexia = person can read words phonetically but has difficulty reading irregularly spelled words by the whole word method e.g. yacht.

Showed surface dyselxic readnword pair they wouldnt know if it was fruit or two.

Can do phenetic reading but not whole word reading.

Phonological dyselxia

Reading disorder which a person can read familiar words even ones that have irregular spellings but has difficulty reading unfamiliar words or pronounceable non words

Damaged brain parts for dyslexia

Whole word reading = ventral stream of the visual system and VWFA.

Phonetic = temporoparietal cortex. Produces the sounds associated with each letter or symbol.

VWFA

Temporal lobe