Brain and language

Dendrites

Receive chemical signals from other neurons via synapses and convert them into electrical impulses

Cell body/soma

Integrate incoming signals from dendrites and determines whether to pass the signal along the axon

Axon

Transmits electrical impulses (action potentials) away from the cell body, towards other neurons or muscles. The speed of transmission depends on myelination

Axon terminals

Release neurotransmitters into the synaptic cleft to communicate with other neurons

Motor neurons

Responsible for movement. Begin in the CNS, travel down the spinal cord and end on muscle fibre.

Sensory neurons

Responsible for senses. Begin at sense organ and convey information to the brain through the spinal cord.

Interneurons

Interposed between other neurons and do much of the computation in the brain

Glial cells

Act as scaffolding and support for growing and repairing neurons

Resting potential of a neuron

When the inside of an axon is negative with respect to the surface by about -70 millivolts. This occurs when a neuron is uncommunicative.

Action potential

An abrupt, short-lived reversal in the electrical charge of an axon when a pulse is applied that exceeds the excitation threshold (-55 millivolts). This causes the inside to swing positive relative to the outside.

Synapse

Where one neuron meets another. The transmission of an action potential along one neuron may cause the next neuron to fire (excitation) or it may inhibit firing (inhibition). Governed by the release of neurotransmitters.

Synaptic reuptake

Neurotransmitters don't sit in the synapse - enzymes come and deactivate neurotransmitters so they are no longer active. They are then used in synaptic reuptake.

Ways drugs can affect the synapse

Stimulate or inhibit neurotransmitter release, stimulate or block postsynaptic receptor molecules, inhibit reuptake.

Central Nervous system components

Brain and spinal cord

Divisions of the peripheral nervous system

Somatic and autonomic nervous systems

Somatic nervous system components

Afferent, efferent and cranial nerves

Afferent nerves

Sensory nerves - transmit information from sense organs to the brain and spinal cord

Efferent nerves

Motor nerves - transmit information from the CNS to effectors (organs of action)

Cranial nerves

Control movements of and carry sensation from the head and neck, regulate glandular secretions in head, control visceral functions. An example of a disorder they are implicated in is photic sneezing, Bells Palsy

Autonomic nervous system

Controls automatic processes, regulation of viscera

Olfactory bulbs

Protrusions on animals brains, such as rabbits and rats, important for smell

Why do some animals have smooth brain surfaces, while humans have wrinkled brain surfaces?

Humans have many more cognitively complex capabilities

Similarities between human and animal brains

All brains have a left and right hemisphere, separated by a longitudinal fissure

Cerebellum functions

Balance/posture, sequencing and timing of precise skilled movements

Damage to the cerebellum

Wide stance/staggering gait (due to lack of balance), tremors during movement and inability to perform rapidly alternating movements, influences thinking and impairs performance of tasks requiring exact sequencing

Pons functions

Arousal, relays sensory information between cerebellum, cerebrum and other parts of the brain, regulates respiration, involved in sleep and dreaming

Medulla function

Regulation of heart rate, blood pressure, rate of respiration, also involved in vomiting, defecation, reflexes and swallowing.

Midbrain functions

Auditory and visual stimuli (eg. eye movement), controls movements used in sexual behaviour and fighting, decrease sensitivity to pain.

Forebrain - cortex

Wrinkled in humans, the outer shell of the brain and is most important for psychological functions

Cortex functions

Tasks performed by the limbic system or midbrains in non-mammals are performed by the cortex in mammals, relay station for information

Gyrus

A ridge.

Precentral gyrus/primary motor cortex

Primary motor gyrus, area that deals with basic movement. Mapped upside down onto the motor cortex, finer movements are allocated more space.

Postcentral gyrus

Primary somatosensory gyrus, deals with sensation

Sulcus

The groove between the ridges, also known as a fissure

Central sulcus

Separates the frontal from the parietal lobe

Thalamus

Receiving & relay station for sensory input. Receives sensory information from the sense organs, performs simple analyses and passes results on to the primary sensory cortex.

Hypothalamus

Homeostasis, controls much of the activity of the autonomic nervous system

Basal ganglia

Regulation and smoothing of movement, beside the thalamus

Limbic system

Amygdala, hippocampus

Amygdala

Expression of emotion

Hippocampus

Memory

Occipital lobe function

Receives input from the eyes, vision

Parietal lobe

Important for spatial perception

Temporal lobe

Receiving area for auditory information

Frontal lobe

Responsible for motor output, motor planning

What is EEG

Measurement of differences in electrical activity across the skull to make inferences about the underlying cortical structures

How is an EEG done?

Electrodes are embedded in a net or cap which is put on a person’s head.

What is being measured in an EEG?

Signal (the electrical activity related to a process or cognition) and noise (the electrical activity related to everything that’s not the signal)

EEG clinical applications

Identification and study of epilepsy, research on the stages of sleep, can help find markers of psychiatric disorders

Strengths and weaknesses of EEG

Good temporal resolution, bad spatial resolution

What does MRI do?

Generates an image of the structure of the brain

What is MRI useful for?

Research and detecting abnormalities in the brain and body

What is an MRI scanner?

A big magnet, image resolution can vary based on magnet strength and size of voxels you are recording

What is MRI measuring?

Protons spin with random orientation within the tissue. When the strong magnetic field is applied, the proton orientation aligns. An external radio frequency pulse un-aligns the protons from the magnetic field. As protons re-align, they release energy that is recorded by the scanner.

What does fMRI measure?

Neuronal activity causes localised changes in blood flow, higher activity = increased demand for oxygen = increased blood flow and oxygen laden haemoglobin.

Strengths and weaknesses of MRI/fMRI

Good spatial resolution (to see differences in structures/activity in certain structures), bad temporal resolution

Damage to primary visual cortex

Scotoma - ‘hole’ in the visual field, like a blind spot, if damage occurs on left side, right side vision will be lost and vice versa

Damage to primary motor cortex

Hemiplegia (paralysis of one side of the body)

ProsopAGNOSIA

Temporal/occipital lobes, difficulty recognising faces - some people can’t recognise familiar faces and others can’t recognise a face as a face.

Damage to prefrontal cortex

Deficiency in response inhibition, inability to plan/lack of foresight, problems with initiating behaviour/changing strategies, eg. Phinneas Gage (personality)

Prefrontal lobotomy

Surgery disconnected prefrontal areas, patients become docile but cognitively disabled

Apraxia

Frontal lobe, serious disturbances in initiation or organisation of voluntary action, unable to perform well known actions and actions become fragmented and disorganised.

Neglect syndrome

People with right-sided parietal damage tend to neglect the left side of space. Can be visual, auditory or tactual. Problem of attention (hemi-inattention), and an emotional component (denial of any deficit - anosognosia)

Why is neglect asymmetrical?

Right hemisphere controls attention to both sides of space whereas left hemisphere controls attention to right side of space only. Therefore damage to the right hemisphere causes neglect of the left side.

Asymmetrical brain: Right hemisphere dominance

Spatial attention, melody, facial recognition, recognition of natural objects

Asymmetrical brain: Left hemisphere dominant

Language, recognition of manufactured objects, voluntary action

Split brain surgery

Relief of intractable, multifocal epilepsy, separates left and right hemispheres and prevents seizures from spreading through the brain

What can the split brain tell us?

Patients seem quite normal, sometimes patients experience an ‘alien hand’.

Left hemisphere function in the split brain

Can’t name objects or words presented in the left visual field/hand, right brain can understand but not speak.

Callosal agenesis

When people’s corpus callosum doesn’t develop, often paired with other neurological problems. Has neural plasticity, so seem normal.

Language

A system of symbols, sounds, meanings and rules which humans use to communicate

Four aspects of language

Phonology, syntax, semantics, pragmatics

Phonology

Sounds, detecting speech features and categorising the sound as a phoneme

Phonemes

The basic perceptual units of speech. The smallest unit of sound which is combined with others to make meaning

Speech perception

The sounds of language are heard, interpreted and understood

Syntax

Language is governed by a set of rules that specify how words and phrases may be combined in sentences

Descriptive grammar

Describes what people say

Semantics

The meaning of words, signs, symbols, and the relationship between words and how we draw meaning from those words

Morphemes

The smallest units of language that carry meaning. Divided into content and function morphemes

Content morphemes

Bull, charge, quiet, picnic, purple

Function morphemes

The, and, that, a, an, ‘s’, ‘ed’, ‘ing’

Pragmatics

The way language is used and understood in everyday life, influenced by context and world knowledge and focuses on implied meanings.

Language production is generative

The mental grammar generates words and sentences according to systematic principles, unconsciously known by speakers.

Nurture - Language development and conditioning

Skinner (1957), using conditioning principles to result in more vocalisations from the child and be shaped into recognisable words and sentences.

Nurture - reinforcement examples

Exchange of looks, smiles and attention - adult reinforcement of any attempt to engage.

Nature - Universal grammar

Children cannot possibly learn all the words and grammatical rules just from reinforcement. Chomsky claimed we were born with innate linguistic principles and an language acquisition device

Child directed speech

High pitched tone, slow speech, exaggerated intonation - preferred by babies to adult-to-adult talk

Language and infancy - 0-7 months

Crying and cooing

Language and infancy - 4-6 months

Babbling using all sounds

Language and infancy - 6-9 months

Babbling and speech perception becomes much more focused to the ‘home language’ (narrowing of sounds)

Language and infancy - 10-12 months

First words develop, comprehension of single words, production of first word

Over-extension errors

Believing one word can be applied to many different things, eg. ‘Dada’ to mean any male

Under-extension errors

Believing one word means only one specific thing, eg. “car” means the family car, but not other cars

Language and infancy - 18-24 months

Begin using two word phrases

Language and infancy - 2-3 years

Begin using 3 word phrases in the correct order, but may not always use correct inflection

Language and infancy - 4-5 years

Can speak with nearly complete syntax

Language and infancy - 5-7 years

Using and understanding more complex language (including past and future tense, make believe, humour)

Language and infancy - 9 years and older

Understand almost all forms of home language(s)