Perception

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  • Created by: becky_99
  • Created on: 20-12-19 19:04

Subcortex

Regulates the frequency and intensity of motor activity. 

Guides attention and learning.

The brain's sensory relay for all senses except smell.

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Limbic system

A region of subcortex involved in regulating the organism to its present and past environment; limbic structures include the amygdala, hippocampus, cingulate cortex, and mamillar bodies.

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Cerebellum

Responsible for the integration of motor commands to promote the smooth execution of improvement.

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Subcortical areas of the brain

Suggested functions of each of these brain areas:

  • Thalamus - sensory relay
  • Basal ganglia - motor processes, attention (Parkinson's disease)
  • Limbic system - emotion and memory
  • Cerebellum - fine-tune motor output
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Intelligence and the brain

Cortex - 4 lobes:

  • Frontal - motor, planning, inhibition, social processing
  • Parietal - sense of touch, spatial attention
  • Occipital - vision
  • Temporal - memory, emotion

Subcortex:

  • Thalamus - sensory relay
  • Basal ganglia - motor processes, attention
  • Limbic system - emotion, memory
  • Cerebellum - fine-tune motor processes
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What determines neuron function?

Shape.

  • E.g. dendrite density

Size.

  • Axon length
  • Axon width: speed
  • Myelin sheath present: speed

Spatial arrangement.

  • Sensory: dendrite in periphery; axon toward brain
  • Motor: dendrite from brain; axon toward periphery
  • Interneurons: neuron-to-neuron connections

Neurotransmitters.

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Roth & Dicke (2005)

Defined intelligence as cognitive and behavioural flexibility.

Bodyweight vs. absolute brain weight.

The bigger the body, the bigger the brain:

  • Neuron density was much higher in humans than other mammals
  • They discussed the potential for human brains to have a higher number of synapses than other mammal brains
  • The authors suggested that the number of cortical neurons could be an indicator of intelligence

Two things that do seem to correlate with behavioural and cognitive flexibility:

  • Number of cortical neurons
  • Speed of axon conduction of cortical neurons

It suggests that processing capacity is important.

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Roth & Dicke (2005)

Problems with this review:

  • The review mainly used data that compared human brains with the brains of other mammals
  • What about differences in intelligence when comparing humans vs. other humans?

Recent evidence suggests that higher number of neurons correlates with a lower IQ (Genc et al., 2018).

Genc et al. (2018) found that those with higher IQs had less neurons per squared measurement.

Conclusions:

  • The authors argued that the neurons ability to prune unused dendritic branches in order to maintain the neural efficiency hypothesis of intelligence; intelligence is not as a result of how hard the brain works but rather how efficiently it works
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Perceptual-motor systems

Sensation is receiving the information from sensory sources.

Perception is elaborating on and interpreting the sensory stimulus.

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The 5 physical senses

The sense and the type of energy detected from it:

  • Vision - light
  • Touch (tactile, somatosensory) - pressure, texture (mechanical) and heat
  • Hearing (audition) - sound, vibration (mechanical)
  • Taste - chemical
  • Smell (olfaction) - chemical
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Proprioception; kinaesthetic sense

Sense of body position and movement of the body:

  • Afferent impulses from stretch receptor to the spinal cord
  • Efferent impulses to alpha motor neurons cause contraction of the stretched muscle that resists/reverses the stretch
  • Efferent impulses to antagonist muscles are damped (reciprocal inhibition)
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What is the purpose of having sensory systems?

Functions:

  • Detect external and internal environments
  • Trigger actions; protect self
  • Receive feedback about own actions
  • Communicate

Sensory systems are closely linked with motor systems.

The full system that detects stimuli (sensory system) and responds (motor system) can be called:

  • Perceptual-motor system
  • Sensorimotor system
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The stretch reflex

  • Muscle spindle senses stretch
  • Sensory neuron conducts action potential
  • Sensory neurons synapse with alpha motor neuron and interneuron
  • Alpha motor neuron to quadriceps is stimulated while the alpha motor neuron to the hamstring is inhibited
  • The quadriceps contract and the hamstrings relax
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What areas of the human brain specialise in sensor

Subcortical area?

  • Thalamus - processes and relays sensory information to the cortex
  • Cerebellum - processes sensory feedback to fine-tune motor processes

Vision - primary visual cortex - occipital lobe.

Touch - primary somatosensory cortex - parietal lobe.

Hearing - primary auditory cortex - temporal lobe.

Smell - frontal lobe.

Taste - gustatory cortex - temporal and frontal lobe.

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Perception

What is "out there" is not necessarily what we perceive "in here".

Suggests:

  • The visual system "processes" the signals from the external world
  • Visual system makes "best" guess based on available information 
  • We need to understand how the "processing", and the "guesses" work, to understand performance
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The eye

Retina:

  • Located at the back of the eye
  • Contains the photoreceptors
  • Photoreceptors are neurons that detect light. If sufficient light strikes them, an action potential occurs

Fovea:

  • Small depression in the retina
  • Detects light from the centre of the visual field
  • Visual field = the area of space that can be seen by the eye

All neurons: photoreceptors, bipolar cells, and ganglion cells are neurons.

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Two types of photoreceptors

Rods:

  • Detect dim light and are specialised for night vision
  • Not present in fovea
  • Achromatic (colour blind)
  • Have low acuity

Cones:

  • Are specialised for day vision
  • Are concentrated in fovea
  • Mediate colour vision
  • Provide greater temporal and spatial resolution than rods

Light activates visual pigments in the outer segments of rods and cones, which causes the receptor to fire.

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Ganglion cells

Ganglion cells are cells in the retina, after rods and cones, in the chain of neurons.

Two types:

  • Parvocellular neuron
  • Magnocellular neuron
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Parvocellular neuron

Small cells.

Small receptive field.

Slow conduction rate.

Colour sensitive.

Concentrated in fovea.

Important for:

  • Detailed form analysis
  • Spatial analysis
  • Colour vision
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Magnocellular neuron

Large cells.

Large receptive field.

Fast conduction rate.

Colour blind.

Concentrated in periphery.

Important for:

  • Motion detection
  • Temporal analysis
  • Depth perception
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How does information get from the eye to the brain

  • Light bounces off an object and hits photoreceptors in the eye which are specialised neurons
  • Photoreceptor fires, sending a signal to the next layers of neurons in the eye, bipolar neurons and ganglion neurons
  • Axons of ganglion neurons exit the eye via the optic nerve and go to the thalamus area of the brain
  • Neurons in the thalamus send the signal to the primary visual cortex of the brain, where the initial processing of the visual information takes place
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