Altered Perceptual Experiences

Question 1

Disorders of perception are divided into:

Answer 1

Sensory distortions (change in the intensity, spatial form, or quality)
Sensory deceptions (a new perception)

Question 2

Sensory distortions

Answer 2

Change in intensity:

Hyperaasthesia (increased intensity of sensations) can occur with intense emotion.
Hyperacusis (increased intensity of noise) occurs with hangovers, migraine, and anxiety.
Hypoacusis (decreased intensity of noise) is seen in delirium.

Change in quality:

Gustatory changes with lithium (metallic taste).
Derealisation.
Chromatopsia (visual aberration in which objects appear abnormally coloured).
Pelopsia (vision perception disorder in which objects appear nearer than they actually are).
Teleopsia (objects appear to be farther away than they actually are).

Changes in spatial form (change to perceived shape of an object):

Micropsia (object appears smaller).
Macropsia (object appears larger).
Dysmegalopsia (object appears larger on one side than the other) can occur with parietal and temporal lobe lesions. Rarely it can be seen in schizophrenia.
Metamorphosia (object appears irregular in shape).

Question 3

Sensory deception

Answer 3

These include illusions and hallucinations.

Illusions:

An illusion is an altered perception of a stimulus and differs from a hallucination in that in hallucinations there is no stimulus.

There are three main types of illusion described in Fish’s clinical psychopathology:

Completion illusions describe the tendency to fill in missing information in order to make sense of a stimulus

Affect illusions arise due to specific mood (affective) states e.g. a woman is walking home in the dark and is frightened, she mistakes a tree for a tall man in a long coat. Another example is an agitated person misinterpreting innocent gestures as threatening.

Pareidolic illusions arise when detailed images are seen from shapes. E.g. seeing the man in the moon, or Jesus Christ on a piece of burnt toast.

Pareidolic illusions tend to occur when a person is concentrating whereas affect and completion illusions occur during inattention.

Hallucinations:

A hallucination is a perception in the absence of a stimulus.

Types of hallucination include:-

Auditory - These can be first person (aka gedankenlautwerdenor echo de la pense) where a patient hears their own thoughts, second person where a patient hears a voice talk directly to them, or third person where a patient hears voice having a discussion.

Visual - These are more common in organic condition such as temporal lobe epilepsy and drug intoxication.

Gustatory - These refer to hallucinations of taste

Olfactory - These refer to hallucinations of smell

Tactile (haptic) - There refer to false perceptions of touch

Functional hallucinations - A patient experiences an hallucination at the same time as receiving a real stimulus in the same sensory modality

Extracampine hallucination - These are hallucinations beyond the possible sensory field

Reflex hallucinations - These occur in one sensory modality in response to a real stimulus in another sensory modality

Hypnopompic hallucinations - These occur as a patient is waking from sleep (these are normal experiences)

Hypnagogic hallucinations - These occur as a patient is going to sleep (these are normal experiences)

Lilliputian hallucinations - These are visual hallucinations whereby the patient experiences seeing people who appear reduced in size or dwarfed

Kinaesthetic hallucinations - These relate to hallucinations of muscle or joint sense. Patient’s may describe that their limbs are being twisted or bent, or their muscles squeezed. They may also described being rocked about

Autoscopic hallucinations - This refers to a person’s experience of seeing a double of themselves in extrapersonal space without the experience of leaving ones body (no disembodiment).

Question 4

Palinopsia

Answer 4

This is a description of palinopsia which refers to a persistence of an image even though the stimulus has gone. They tend to suggest an organic pathology.

Question 5

Synaesthesia

Answer 5

In synaesthesia a sensation in one modality produces a sensation in another modality. If is often described as a ‘union of the senses’. It occurs in 1% of people and is a harmless condition

Question 6

Echo de la pense

Answer 6

Echo de la pense is also known as thought echo and gedankenlautwerden. It describes the experience of hearing one’s own thoughts and is a first rank symptom seen in psychosis.
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Question 7

Brodnignagian hallucination

Answer 7

Also known in the literature in the (misspelled) variants brobdignagian hallucination and brodnigagian hallucination. The term brobdingna-gian hallucination is indebted to Brobdingnag,the name of a fictitious country inhabited by huge people, featuring in the novel Gulliver’s Travels by the Irish poet and author Jonathan Swift (1667-1745). It is used as a synonym for the term *gulliverian hallucination, i.e. a *visual hallucination in which disproportionally large human figures are perceived, either in isolation, or against a background of regular proportions.