Visio-spatial and attentional disorders

Selective attention

- almost always assessed in the visual domain

Neglect patients damage to the right hemisphere

- also signs of decreased non-spatial attention - deficits in alerting, arousal, attention

Functional electrical stimulation (FES)

- apparatus, which delivers electrical stimulation to muscles, enabling automatic contraction or relaxation, without the need for self-generated motor commands

Prism segments

- approach to compensate for visual field loss -> shifts visual information that would otherwise fall in the damaged area of the visual field into intact regions

Alertness and sustained attention

- capacity to maintain a readiness to respond -> can be measured by comparing reaction times between warned and unwarned trials

Confrontation technique

- crude assessment of visual field disorder -> focusing at examiners nose while detecting small movements in examiners finger's

Greyscales test

- distinguishes between perceptual and motoric aspects of neglect -> patients decide which of two rectangles, each shaded incrementally from black to white, is darker

Training leftward scanning

- exploration of the left side is encouraged -> but positive results are specific to task and not generalizable

Caloric vestibular stimulation (CVS)

- increases leftward scanning - improves motor function, tactile sensation, -> canal of one ear is chilled with cold water, triggers a mechanism that compensates for head movements by moving the eyes in the opposite direction

Neglect in imagery

- milanese patients, famous scare from a city

Limb activation training Functional electrical stimulation of the contralateral hand

- movement of left limbs within left space reduces omissions on a spatial task

allesthesia or allochiria

- neglect patient may show a degree of contra-positioning (e.g. transfers elements of the stimuli from the left side to the right side, all numbers of the clock on the right side)

spontaneous recovery

- occurs in 12-30% of patients, further improvements may continue -> complete recovery relatively rare

Extinction

- patient is perfectly able to identify a stimulus presented in isolation -> trouble when more stimuli are presented

Line bisection

- patients presented with plain horizontal lines -> asked to judge and mark the midpoint (healthy individuals, slightly leftward error) (neglect patients -> deviates markedly from the middle)

Bilateral hemispheric damage

- produces impairments in both visual fields -> can lead to tunnel vision

Induced shifts of attention to the left

- promotes leftward scans by making patients wear glasses with patches over the right half of each lens -> improvement

Multimodel distortions

- suggest neglect (auditory, visual, sensory, ....)

Reading and writing with neglect

- tend to omit beginnings of words, sentences - writing often only on the right-hand of the page

Rehabilitation methods of neglect

- training leftward scanning - induced shifts of attention to the left - caloric vestibular stimulation (CVS) - mechanical vibration of muscles - prism lens adaption - limb activation training - functional electrical stimulation of the contralesional hand - functional electrical stimulation (FMS)

2 key principles of attention

1. brain systems for attention are separable from perceptual processes 2. Within the attention system, different networks perform different functions - alertness / vigilance - target selection / focused attention - orienting / spatial attention

Assessment of neglect

Easiest: observation in a naturalistic setting -> person ma fail to dress, wash one side of the body, only eat half of their plate of food, ignore persons standing on their left side (most patients also lack insight)

Dorsal stream

Where stream (How stream)

Cancellation tasks

assessment of neglect - cross out visual targets scattered across a paper sheet (neglect patients miss many targets on the neglect side)

Tunnel vision

blindness to all but the central region of space

Non-spatial forms of attention

difference between two levels of attentional difficulty in the same task - > Stroop task -> Performance deterioration of a dull task Assessment: - observing subjects in daily life - look at general ability (IQ)

anosognosia

unawareness of denial of illness (usually occurs with patients with left unilateral neglect, do not accept they have neglect, confabulate)

Perimetry

used to assess visual field disorders - patient asked to fixate at the center of a uniformly illuminated hemisphere and report when a light stimulus brought from the periphery towards the center of display becomes visible -> through repetition a map of the patients vision can be created

Ventral stream

what stream - object recognition

Unilateral spacial neglect

difficulty in detecting, acting on, imagining information from one side of space -> often seen as a disorder of attention -> main cause is cerebrovascular disease (stroke) -> damage often associated with the parietal cortex -> most patients recover spontaneously, some do not Chronic spatial neglect -> mostly seen in patients with right hemisphere lesions and neglect of the left side Heterogeneous syndrome -> severity and manifestation of the disorder vary from person to person

Quadrantanopia

loss of information form the upper or lower section of a hemifield

Hemianopia

loss of input from a majority of one hemifield (complete damage to one side of the primary visual cortex) ↓ cortical blindness to one side of the visual field

stroke

most common cause of visual field loss

Dual tasks

participants required to divide attention between 2 tasks -> sensitive marker of cognitive deficits

Mechanical vibration of muscles

patients back muscles are unilateral vibrated while performing spatial tasks -> improvement even after 2 months

Wundt-Jastrow Illusion test

patients judge which of 2 arcs are larger (both the same size, but lower arc extending further to the left)

3 spacial representations

personal space - awareness of the location of the sensation from our own body and relative location of the limbs peripersonal space - are in immediate reach of our body. in which most of our actions occur extrapersonal space - wider visual world that lies outside of our immediate reach

scotoma

small islands of blindness within a field (partial damage to V1)