Perception and disorders of perception. Distortions, deceptions and hallucinations. Derealization and depersonalisation.

1. DISORDERS OF
PERCEPTION
Dr Vijay Bhatia
Psychiatrist

2. PERCEPTION
 the ability to see, hear, or become
aware of something through the
senses.
 Awareness derived from sensory
processes while a stimulus is present
 Apprehending by means of the senses
or of the mind

3. DISORDERS OF
PERCEPTION
 Sensory Distortions.
 Sensory Deceptions.

4. SENSORY
DISTORTIONS
 There is a constant real perceptual
object, which is perceived in a
distorted way.
 Changes in intensity
 Changes in Quality
 Spatial form

5. CHANGES IN
INTENSITY
 Hyper-aesthesia
 Hypo-aesthesia

6. HYPERAESTHESIA
 May be result of intense emotions
 Or lowering of the physiological
threshold
 For example – a person may see roof
tiles as brilliant flaming red
 Or hear the noise of a closing door like
a clasp of thunder.

7. CAUSES OF
HYPERAESTHESIA
OR HYPERACUSIS
 Anxiety
 Depressive disorders
 Hangover from alcohol
 Migraine
 These are associated with increased
sensitivity to noise.

8. HYPERAESTHESIA
 Patient suffering with hypomanic
episode
 Suffering with epileptic aura
 Or Under the influence of LSD
 May see colours as very bright and
intense but these can also be a feature
of intense normal emotions such as
religious fervour or the surpassed
happiness of being in love.

9. HYPOACUSIS
 Where the threshold for all sensations
is raised
 E.g. Delirium
 Defects in attention found in delirium
further reduces sensory acuity.
 ADHD
 Depression
 Gustatory and visual sensations may
also be lowered in depression, for
example everything is black, or all
foods taste the same.

10. CHANGES IN
QUALITY
 Mainly Visual – brought about by toxic
substances
 Colouring of yellow – Xanthopsia
 Colouring of Green – Chloropsia
 Colouring of Red – Erythropsia
 Main cause is drugs like poisoning with
Mescaline or digitalis.
 Metallic taste – with lithium

11. DEREALISATION
 Everything appears unreal or strange
 While in mania – objects look perfect
and beautiful.

12. CHANGES IN
SPATIAL FORM
(DYSMEGALOPSIA)
 This refers too a change in the
perceived shape of an object.
 Micropsia – objects are smaller than
they really are.
 Macropsia or magalopsia – objects are
larger than they really are.
 Micropsia also includes the experience
of the retreat of the objects in to the
distance without change in size
although some authors call this as
porropsia.

13. CHANGES OF
SIZE
 Lilliputian hallucinations – in alcohol
withdrawal etc,
 Dysmegalopsia – objects are perceived
to be larger (or smaller) on one side than
the other.
 Or just changes in size perceived.
 Metamorphosia – objects that are
irregular in shape
 Dysmegalopsia can result from retinal
disease, disorders of accommodation
and convergence.
 Commonly from temporal or parietal
lobe lesions and rarely in
 Schizophrenia.

14. CHANGES OF
SIZE
 Scarring of the retina with retraction naturally
produces macropsia or irregular –
metamorphosia
 Complete paralysis of accommodation or
overactivity of accommodation during near
vision is likely to cause macropsia
 While partial paralysis of accommodation will
lead to the experience during near vision that
the object is very near – micropsia will occur.
 If accommodation is normal but convergence
is weakened, macropsia will occur.
 Dysmegalopsia may occur in poisoning with
atropine or hyoscine.

15. CHANGES OF
SIZE
 Hypoxia and rapid acceleration of the
body can disturb accommodation and
convergence.
 Chronic arachnoiditis – dysmegalopsia
 Central lesions mainly affecting the
posterior temporal lobe, epileptic fit –
micropsia, macropsia or irregular
distortions may occur during the aura
or in the course of the fit itself.

16. DISTORTIONS
IN THE
EXPERIENCE OF
TIME
 Happy mood – time passes quickly
 Sad mood – time passes slowly
 In severe depression time passes very slowly and
even standstill.
 In schizophrenia time moves in fits and starts
and may have a delusional elaboration that
clocks are being interfered with.
 In acute organic states –disorders of personal
time are shown in temporal disorientation and in
milder forms there may be overestimation of the
progress of time.
 Patients with temporal lobe lesions complain
that time either passes quickly or slowly.
 In schizophrenia – abnormalities of time
judgement. Age disorientation is present in
chronic schizophrenia.

17. TRAILING
PHENOMENON
 Perceptual abnormalities in which
moving objects are seen as a series of
discreet and discontinuous images.
 They are associated with
hallucinogenic drugs like magic
mushrooms and LSD.

18. THE END
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