Disorders of perception can involve sensory distortions or deceptions such as illusions and hallucinations. Illusions involve misinterpretations of external stimuli while hallucinations involve perceptions without an adequate stimulus. Hallucinations can be classified by sensory modality (auditory, visual, etc.) and cause (organic, psychiatric). Memory disorders can also occur and involve problems with registration, retention or recall of information. Organic causes like head injuries can cause anterograde or retrograde amnesia while psychiatric conditions like depression can impact memory through mood effects. Disorders of perception and memory can provide clues to underlying organic or psychiatric pathologies.

1. Disorders of perception
Mahlet Yared, MD

2. Definition
• Sensation : receiving raw data outside self through peripheral
sensory organs .
• Perception: Transformation of raw data into a meaningful
representation.
• depend on attention, culture , affect , prior experience and
memory.

3. Classification
• Sensory distortion- a constant real perceptual
object is perceived in a distorted way .
• Sensory deceptions – Illusions and hallucination

4. Sensory deceptions
• Illusions :- misinterpretations of stimuli arising from
an external object.
• Hallucinations :- perceptions without an adequate
external stimulus.

5. Illusions
• Stimuli from a perceived object are combined with a
mental image to produce a false perception.
• Illusions in themselves are not indicative of
psychopathology.
• Visual illusions are most common
• Illusions VS Functional hallucinations

6. Types
• Completion illusions: these depend on inattention such
as misreading words in newspapers or missing misprints
because we read the word as if it were complete.
• Affect illusions: arise in the context of a particular mood
state.
• Pareidolia: is a visual phenomenon involving a
stimulus where the mind perceives a familiar pattern of
something where none actually exists
-vivid illusions occuring without making any effort are the
result of excessive fantasy thinking and a vivid visual
imagery.

8. Hallucinations
• False perceptions
• Classified based on their sensory modality
• Elementary/Simple: simple noises, such as banging or hissing
• Complex: voices
• Pseudo-hallucinations are a type of mental image that, although
clear and vivid, lack the substantiality of perceptions; they are
seen in full consciousness, known to be not real perceptions and
are located not in objective space but in subjective space .
• presence pseudo-hallucinations does not necessarily indicate
psychopathology.

9. Causes
• Intense emotions or psychiatric disorder-
depression ,schizophrenia
• Organic causes – TLE, Tumors
• Sensory deprivation Charles bonnet syndrome
• Content tends to be related to the nature of the
disorder

10. Types
• Auditory- important diagnostic significance
organic states : usually unstructured sounds
schizophrenia : commanding, commentary
• Visual - characterstics of organic states
- charles bonnet's syndrome- No other psychotic
features or any evidence of psychiatric disorder
- delirum tremenes - Lilliputian hallucinations
• Olfactory - occurs in schizophrenia ,TLE and in depressive
psychosis.
difficult to distinguish from delusion

11. Hallucinations of bodily sensation
• Haptic hallucinations- may take the form of being touched, painful
or sexual sensations.
Formication is the hallucinatory experience of feeling insects or small
animals crawling on the skin.
Particularly in drug and alcohol withdrawal, notably with the use of
cocaine.
• Kinaestethic hallucination- Involves muscles and joints- e.g. arms
being twisted
Complex deep somatic hallucinations may occur as feelings of viscera
being moved or distended.

12. Hallucinatory Syndromes
• Persistent hallucinations in any sensory modality in
the absence of other psychotic features.
• Alcoholic hallucinosis; usually auditory and occur
during periods of relative abstinence.
• Organic hallucinosis; these are present in 20−30% of
patients with dementia, especially of the Alzheimer
type, and are most commonly auditory or visual
associated with disorientation and memory
impairment .

13. Special hallucinations
• Functional hallucinations -always provoked by a stimulus
in the same modality
seen in chronic schizophrenia e.g. voices from a running
tap water
• Reflex hallucinations -stimulus in one sensory modality
producing a hallucination in another. e.g hearing of voices
associated with particular aroma
• Extracampine hallucinations hallucination that is outside
the limits of the sensory field. e.g hearing some one talk in
another country

14. Autoscopy (phantom mirror-image Autoscopy)
• The experience of seeing an image of oneself in external
space and knowing that it is oneself.
• Associated with epilepsy, focal lesions affecting the
parieto−occipital region and toxic infective states (basal
region of the brain)
• Negative Autoscopy- A few patients suffering from organic
states look in the mirror and see no image.
• Internal Autoscopy in which the subject sees their own
internal organs - rare

15. Hypnagogic and hypnopompic hallucinations
• Occurs when the subject is falling asleep or waking up
respectively.
• Not necessarily indicative of any psychopathology , occur in
narcolepsy
Dissociative hallucinations: usually intense feelings and
knowledge of being in the presence of someone
– can also be applied to hallucinations occurring in two
sensory modalities, e.g. 'the vision that speaks'.
– are normal in bereavement

16. patients attitude towards hallucinations
• In organic hallucinations the patient is usually terrified by the
visual hallucinations and may try desperately to get away from
them.
• Lilliputian hallucinations, which are usually regarded with
amusement by the patient and may be watched with delight.
• In acute schizophrenia become a frightening experience and
the patient at times may attack the person he believes to be
their source.
• In chronic schizophrenia are often not troubled by the voices
• patients with insight may deny hallucinations .

17. The phantom limb
• The most common organic somatic hallucination .
• The patient feels that they have a limb from which in
fact they are not receiving any sensations either because
it has been amputated or because the sensory pathways
from it have been destroyed.
• Occurs in about 95% of all amputations after the age of
6 years.
• Lesions of the parietal lobe can also produce somatic
hallucinations with distortion or splitting-off of body
parts.

18. Body image distortions
• Hyperschemazia: perceived magnification of body parts can
occur in organic and psychiatric conditions.
• The perception of body parts as absent or diminished is
known as aschemazia or hyposchemazia respectively and is
most likely to occur in parietal lobe lesions
• Paraschemazia or distortion of body image is described as a
feeling that parts of the body are distorted or twisted or
separated from the rest of the body and can occur in
association with hallucinogenic use, with an epileptic aura and
with migraine on rare occasions.
• Hemisomatognosia is a unilateral lack of body image in it
occurs in migraine or during an epileptic aura.
• Anosognosia ‘denial of illness’ - patients who had stoke
denied the hemiplegia

19. Sensory distortions
• Changes in intensity (hyper- or hypo-aesthesia)
hyperaesthesia :-increased intensity of sensations
can result from intense emotions or a lowering of the
physiological threshold.
hyperacusis - is a disorder in loudness perception
Anxiety , depressive disorders , hangover from alcohol and migraine
Hypoacusis occurs in delirium, where the threshold for all sensations is
raised. The defect of attention found in delirium further reduces sensory acuity.

20. Changes in spatial form (dysmegalopsia)
• Change in the perceived shape of an object.
• Micropsia is a visual disorder in which the patient
sees objects as smaller than they really are.
• The opposite kind of visual experience is known as
macropsia or megalopsia.
• Dysmegalopsia can result from retinal disease,
disorders of accommodation and convergence most
commonly from temporal and parietal lobe lesions.
• Rarely, it can be associated with schizophrenia.
dysmegalopsia may occur in poisoning with atropine
or hyoscine.

21. Distortions of the experience of time
• varieties of time could be physical and personal
• personal judgement of the passage of time important
in psychiatric disorders.
• affected by mood states , temopral lobe lesions ,
scizpohrenia

22. Disorders of Experiences of self

23. Disturbance of awareness of self-
activity
• There are two aspects to the sense of self-activity:
- the sense of existence
- the awareness of the performance of one’s actions

24. Depersonalization
• The individual feels as if he/she is unreal
• Not an experience of unreality
• schizophrenia, depressive illness, organic brain
disease or substance misuse
• Affect is always involved , insight is preserved
• The experience usually hard for the individual to
elaborate and also for the clinician to portray

25. Disorder of being or ego vitality
• The patient’s experience of his very existence may be
altered
• ‘I do not exist, there is nothing here’ or ‘I am not
alive any more’ or ‘I am rotting
• Nihilism

26. Disturbances of the boundaries of the
self
• Ego demarcation
• The disturbance in knowing where I ends and not I
begins.
• Loss Ego boundary
• Seen in schizophrenia , LSD intoxication

28. Disorders of Memory

29. Mechanism of Memory
• Sensory Memory
- Initial and early phase of memory
- a selecting and recording system via which
perceptions enter the memory system
- Fleeting visual image
- If not further processed as short term memory it
decays

30. • SHORT-TERM MEMORY
- a simple span of attention limited to six or seven items
and lasting 15 to 30 seconds unless the items are
rehearsed.
Consists of
- Central Executive- attention controller
- A visuospatial scratch pad – temporary storage and
manipulation of visual and spatial information
- a phonological loop - holds memory traces of verbal
information

31. • Long term Memory
Two retrieval system
Declarative system, or explicit memory – semantic (fact
memory) and episodic (memory for specific
autobiographical incidents)
Implicit memory – procedural memory

32. • Memory has three components: registration, retention
and recall.
• Registration- may be impaired with alcohol, anxiety
or after head injury.
• Retention- is abnormal after head injury, in dementia,
Korsakoff's syndrome or in any organic disorder
causing bilateral hippocampal damage.
• Recall -may be impaired in organic disorders but this
is more typical of a psychogenic amnesia, e.g.
anxiety, affective or dissociative disorders.

33. Organic amnesias
Acute brain disease
• Memory is poor owing to disorders of perception and
attention.
• Failure to encode material in long-term memory.
• Retrograde amnesia- embrace the events just before the
injury. This period is usually no longer than a few minutes
but occasionally may be longer, especially in subacute
conditions.
• Anterograde amnesia -Impairment is seen as the failure of
retrieval of information encountered after the onset of a
clinical disorder. These occur most commonly following
accidents and are indicative of failure to encode events into
long-term memory.

34. Blackouts - are circumscribed periods of anterograde amnesia
experienced particularly by those who are alcohol dependent
during and following bouts of drinking.
• indicate reversible brain damage and vary in length but can
span many hours.
• also occur in acute confusional states (delirium) due to
infections or epilepsy. Subacute coarse brain disease
• characterized by the inability to learn new information
(anterograde amnesia), and the inability to recall previously
learned material (retrograde amnesia).

35. Confabulation - falsification of memory occurring in clear
consciousness in association with organic pathology. It
manifests itself as the filling-in of gaps in memory by
imagined or untrue experiences that have no basis in
fact.
• a falsely retrieved memory
• The patient is unaware that he or she is confabulating
and often unaware of the existence of memory deficit.
• Patients may act on their confabulation, confirming
their belief in the false memory.
• Confabulation is most apparent in autobiographical
memory.

36. Pseudologia fantastica
• fluent plausible lying (pathological lying)
• describe the confabulation that occurs in those
without organic brain pathology such as antisocial
personality
• describes various major events and traumas or
makes grandiose claims and these often present at
a time of personal crisis, such as facing legal
proceedings.
• Blurred boundary between fantasy and reality,
when confronted with incontrovertible evidence
these individuals will admit their lying.

37. Munchausen’s syndrome
• A variant of pathological lying in which the individual
presents to hospitals with bogus illnesses, complex
medical histories and often multiple surgical scars.
• A proxy form of this condition has been described in
which the individual usually a parent, produces a
factitious illness in somebody else, generally their
child. This may lead to repeated presentations to
hospital over a prolonged period of time
• The role of suggestibility is important in those who
present with confabulation, pseudologia, retrospective
falsification or false memory.

38. Vorbeireden(approximate answers)
• Described by Ganser (Ganser state)
• Ganser described four criminals who showed
1.clouding of consciousness with disorientation,
2.auditory and visual hallucinations (or pseudo-hallucinations),
3.amnesia for the period during which the symptoms were manifest,
conversion symptoms and recent head injury
4.infection or severe emotional stress.
• Approximate answers suggest that the patient understands the questions but
appears to be deliberately avoiding the correct answer.
• Ganser believed it to be a hysterical condition with the unconscious
production of symptoms to avoid a court appearance.
• It is believed that the Ganser syndrome is indicative of either an organic or
a psychotic state rather than hysteria as originally believed.
• Ddx – malingering and factitious disorder

39. Affective disorder of memory
• Memory is also affected by emotion.
• Affective state strongly influences the processes of
remembering and forgetting.
• Mood disorders – associated with impairment in
cognitive processing
• Depression- Self reported memory impairment
• Memory bias for affectively toned material, such that
information that has an emotional valence is more
likely to be retrieved if it is congruent with the
individual’s mood during retrieval.

40. Thank You