agnosiacompile

What is Agnosia?: 

What is Agnosia ? Means “without knowledge” Perceptual disorder sensation is preserved ability to recognise a stimulus or know its meaning is lost Patients cannot understand or recognise what they see, hear or feel Results from lesions disconnect and isolate visual, auditory and somatosensory input from higher level processing

Types of Agnosia: 

Types of Agnosia Auditory agnosia inability to recognize or differentiate between sounds in the absence of defect of the ear neurological inability of the brain to process what the sound means

Types of Agnosia: 

Types of Agnosia Visual agnosia difficulty in recognising visually presented objects in the absence of impairment of primary visual and intellectual functions Apperceptiveagnosia perceptual analysis of the stimulus Associative agnosia association between the conscious percept and its meaning

Types of Agnosia: 

Types of Agnosia Tactile agnosia inability to recognize objects by touch, despite relatively preserved primary and discriminative somesthetic perception

Types of Agnosia: 

Types of Agnosia Alexithymia difficulties in differentiating one's feelings and expressing them in words.

Types of Agnosia: 

Types of Agnosia Time agnosia inability to understand and comprehend the passage of time

Auditory Agnosia: 

Auditory Agnosia

Auditory Agnosia: 

Auditory Agnosia Inability to recognize or differentiate between sounds. Loss of the normal ability to derive the meaning from an auditory stimulus . Neurological inability to process what the sounds mean

Auditory Agnosia: 

Auditory Agnosia Linguistic Verbal Information agnosia Wernicke’s area agnosia Classical / pure auditory agnosia Interpretive / receptive agnosia

Linguistic Agnosia: 

Linguistic Agnosia Pure word deafness Lesions to the Wernicke’s Area of the brain Subjects cannot comprehend words S ign language Reading books Able to speak

Classical Agnosia: 

Classical Agnosia Non-verbal auditory agnosia Inability to process environmental sounds More commonly reported in cases of bilateral or unilateral left hemisphere lesions

Classical Agnosia: 

Classical Agnosia Sound motion perception Hemifield contralateral to hemispherectomy . Right or left parieto - temporo -insular lesions. Auditory spatial functions Circumscribed hemispheric lesions

Causes: 

Causes Cerebrovascular disease Midportion of the first temporal gyrus bilaterally Unilateral damage Posterior temporal lobe of the hemisphere dominant for speech Residual abilities present depend on right hemispheric linguistic abilities. Primary auditory cortex  pure word deafness Auditory association cortex  non-speech sounds Both regions  global auditory agnosia

Interpretive/receptive agnosia: 

Interpretive/receptive agnosia Amusia Inability to understand music Deficit of rhythmic ability Distrimbria Regard music as noise Vocal singing as ‘odd tone of voice’

Visual Agnosia: 

Visual Agnosia ApperceptiveAgnosia Cannot copy a design or match an object or a figure to a sample. Associative Agnosia Cannot recognise or name an object but they can copy it, name it from verbal description

2 forms of agnosia: 

2 forms of agnosia The copying abilities of individuals with (a) apperceptive agnosia and (b) associative agnosia.

Slide 17: 

ApperceptiveAgnosia ApperceptiveAgnosia Cannot copy a design or match an object or a figure to a sample. Extreme cases - visual form agnosia Bilateral damage to the lateral occipital lobes , critical structures involved in visual perception Preservation of elementary visual functions Accurately interact with objects around them and maneuver through their environment Intact mechanisms in the dorsal stream

Associative Agnosia: 

Associative Agnosia Perception remains intact, that is, it becomes inaccessible Dissociation between the mechanisms underlying visual perception and those that provide access to the semantic information associated with objects Biological items depending on specialized neural mechanisms that are unused (or underused) when recognizing objects Inferior–temporal lobe damage Associative Agnosia

Tactile agnosia: 

Tactile agnosia

The Tactile System: 

The Tactile System . Largest sensory system in the body . Perceives touch, texture, mechanical consistency, heat, cold, and pain . Touch information is processed in the cortex . Tactile information and proprioception contribute to the representation of an object

Tactile Agnosia: 

Tactile Agnosia Impairment in building the object representation Two types that vary in the level at which abnormality in information-processing occurs: 1. Tactile ApperceptiveAgnosia 2. Associative Tactile Agnosia

Tactile ApperceptiveAgnosia: 

Tactile ApperceptiveAgnosia Problems concerning the perception and integration of micro or macrogeometrical properties Can be feature-specific e.g. difficulty integrating texture information

Associative Tactile Agnosia: 

Associative Tactile Agnosia Representation of features are accurate, but fail to generate the semantic knowledge of the object Basic and intermediate somaesthetic functions are preserved, but complex function is impaired Patients can describe the object, but they cannot identify it after touching it This form of tactile agnosia is rarely identified

Treatment and recovery : 

Treatment and recovery → Physical and Occupational Therapy → Principles of treatment : 1. Restitution, 2. Repetitive training of impaired function 3. Compensation by utilisation of spared function to compensate for the deficit.

Feelings: 

Feelings

Alexithymia: 

Alexithymia A state of deficiency in understanding, processing, or describing emotions (Peter Sifneos , 1972 ) Not a mental disorder in the DSM-IV The conception of alexithymia has been evolving in the academic literature. Dimensional personality trait 2 types Primary Secondary

Alexithymia: 

Alexithymia Reduced ability to: identify and describe one’s own feelings Distinguish feelings from the bodily sensations of emotional arousal and impaired symbolization F ocus on external events rather than inner experiences Sifneos (1972 )

Assessment: 

Assessment Standardised assessment  S elf-report questionnaires 20-item Toronto Alexithymia Scale (TAS-20 ), Bermond -Vorst Alexithymia Questionnaire (BVAQ )

Alexithymia - Neurology: 

Alexithymia - Neurology Several neurological models Disconnect between the limbic and neocortical areas . R educed interhemispheric communication Dysfunction of the right hemisphere D eficiency in the activation of the anterior cingulate cortex (ACC) during emotional processing

ACC: 

ACC Part of the brain’s limbic system Resembles a "collar" form around the corpus callosum Further divided into two subsections Dorsal – Cognitive division Ventral – Affective division

ACC: 

ACC Image Source: Bush, G., P. Luu , et al. (2000). "Cognitive and emotional influences in anterior cingulate cortex." Trends in Cognitive Sciences 4 (6): 215-222.

ACC and Alexithymia: 

ACC and Alexithymia Gündel et. al Significant positive relation between size of right ACG and alexithymia as measured with TAS-20 scores Research by Kano et. al Measured rCBF in brain regions of alexithymics and non- alexithymics Results Alexithymics have less activation in the ACC ACC less activated in alexithymic’s response to angry faces

The Right Hemisphere: 

The Right Hemisphere Brain regions where rCBF was lower in the alexithymics than in the non- alexithymics were localized in the right hemisphere rCBF readings in right hemisphere correlate negatively to TAS-20 scores 1. orbitofrontal cortex

Treatment: 

Treatment Insight orientated treatments are counter productive M ore cognitive behavioural therapy like patients No direct medication Self-help?

Time Agnosia: 

Time Agnosia

Slide 36: 

What is time? Phylogenetic (evolutionary) Philosophical/spiritual gnosis (understanding) Ontogenetic (developmental) Pavlov’s experiments Children have difficulty forming a trace-reflex Understanding of time only fully established at age 14

Stages of the understanding of time: 

Stages of the understanding of time 1. appreciation of rhythm 2. estimation of appreciation of short intervals of time 3. appreciation of the flow of time 4. appreciation of chronology 5. appreciation of present, past and future

Slide 38: 

Basal ganglia (Internal timekeeper) Time a wide range of intervals (ms to s ) Striataldopaminergic neurotransmission involved in internal timekeeping Thalamus (Attention) Activated during the encoding of intervals Coupled activation in the right inferior parietal cortex Interdependence with attention Neurological patients with right inferior parietal damage show time perception deficits in line with attention impairment Bilateral premotor and right DLPF cortex (Memory) Involved with temporary storage function

Agnosia: 

Agnosia Takes many forms Auditory Visual Tactile Alexithymia Time Each form has multiple causes and can affect multiple regions of the brain

Thank You: 

Thank You