The Activation Synthesis Theory of Dreaming (OCR GCSE Psychology): Revision Note

A neurobiological explanation of dreaming

• Hobson & McCarley proposed a neurobiological explanation of dreaming called the activation synthesis theory

  • They rejected Freud’s idea that dreams contain hidden meanings

• They argued that dreams are:

  • the brain’s attempt to make sense of random neural activity

  • shaped by whichever memories or emotions are activated in the moment

  • produced mainly during REM sleep

  • the result of activation from the brainstem and synthesis by the cerebral cortex

The role of REM sleep

• Dreams mainly occur during REM sleep, when:

  • brain activity becomes highly active

  • eyes move rapidly

  • breathing becomes quicker and irregular

  • muscles are temporarily paralysed

• Brain scans show sudden spikes of electrical activity just before and during REM. These spikes:

  • activate the cerebral cortex

  • trigger memories, images and sensations

  • lead the brain to construct a dream to make sense of the signals

• Because many brain areas are activated at once, dreams often feel:

  • bizarre

  • fragmented

  • constantly shifting

Activation: what the brain does during REM sleep

Pons activity

• The pons sends random electrical bursts during REM sleep that:

  • move the eyes

  • activate the limbic system

  • stimulate the visual cortex in the occipital lobe

  • trigger stored memories and emotions across the brain

• These signals are random, not purposeful

Synthesis: the cerebral cortex

• The cortex attempts to organise the random activation/signals into a meaningful narrative – this process is called synthesis

• The cortex draws on:

  • memories

  • emotions

  • past experiences

  • sensory information

• This produces dreams that are often:

  • strange

  • disjointed

  • illogical

The role of the limbic system

• During REM sleep, the limbic system becomes highly active, which explains why dreams often feel:

  • emotional

  • dramatic

  • intense

• Dreams commonly include fear, excitement, sadness or anger because the brain’s emotional centres are firing

Criticisms of the activation synthesis theory of dreaming

• The theory is reductionist

  • It oversimplifies dreaming by reducing it to random brain activity

  • It doesn't explain dreams that have meaning and continuity that go beyond simple brain activity

• Dreams are not always random

  • Research shows dreams can reflect real-life events, worries and memories ('day residue')

  • Some dreams are structured and meaningful, contradicting the idea of randomness

• Dreams occur in non-REM sleep

  • People report dreams during non-REM stages, too, although they may be less vivid

  • Better recall in REM sleep may simply occur because we wake more often during this stage

• Brainstem damage doesn’t eliminate dreaming

  • Some people with damage to the pons still report dreams

  • This suggests that dreaming involves multiple brain regions, not just the pons