❀ Attention and Consciousness ❀
Attention
Attention: narrowing or focusing awareness selectively to a part of the sensory environment
or to a class of stimuli
- I.e., mental spotlight
Single feature detectionis easy and automatic
- The visual system finds is very easy to detect an object that
deviates on a single feature (color or orientation)
- Attention is mainly driven by the s timulus/input (bottom-up)
Conjunction search : search for a combination (or conjunction
) of two or more features in the
same stimulus (vertical + red)
- Harder (more attention needed)
- Takes longer due to more distractors
- Directing top-down attentionto the objects in order to find the right
combination
Inattention
Inattentional blindness : when a person fails to notice an event that occurs as they are
performing another task
- E.g., a failure to notice a dot flashed on a computer monitor during performance of a
visual task
Change blindness : when a person fails to detect changes in the presence, identity, or
location of objects in scenes
- Most likely to occur when people do not expect changes
Attentional blink: when a person fails to detect a second visual target
presented within 500 milliseconds of the first one
- Attention to the first target prevents awareness of the second one
Sensory neglect : a condition in which a person does not respond to sensory
stimulation
- Parietal lobe lesions
- Damage to the temporoparietal junction → the left side of the
surrounding spaces ceases to exist
- Normally, the right parietal region is engaged when attended stimuli
are in the right or left visual field
- However, the left parietal region is engaged only for stimuli in
the right visual field
- Damage to the right parietal region → no backup; left side of
space excluded from conscious awareness
- Both copying and spontaneous drawing impaired
- Patients with neglect identify the two houses as identical (yet prefer the
right house; meaning is processed)
Consciousness
Consciousness
: responsiveness of the mind to impressions made by the senses
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, - Automatic processesare unconscious
- Occur without intention, involuntarily, without awareness, and without
interfering with ongoing activities
- Bottom-up
- Conscious operationsrequire focused attention
- Top-down
Prerequisites of consciousness:
1. Arousal : waking the brain up via nonspecific neuromodulatory systems
2. Perception : detection and binding of sensory features
3. Attention : selection of a restricted sample of available information
4. Working memory : short-term storage of ongoing events
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, ❀ Brain Development and Plasticity ❀
Development of the Human Brain
Enriched environments contribute to a person’s cognitive reserve
- Higher brain reserve (stronger synapses, more complex connections) → cognitive
reserve
- Each time the brain is challenged (e.g., you take up a music class), it adds to
the cognitive reserve
- Studying also challenges the brain
- Early in life
- The higher the cognitive, the higher the quality of life
- Protected against neurodegenerative diseases (postpone not prevent)
Growth spurts : sudden growth in development that lasts for a
relatively short time
- 3-10 months until 1.5 years
- Increase in brain weight by 30%
- 2-4, 6-8, 10-12, 14-16
- During these spurts, the brain weight increases by
5%-10%
- The brain can recover more
Brain growth coincides with cognitive development
- The white matter connections keep increasing until 25-30
years of age
- Gray matter volume begins declining at 6 to 7 years of age (neuron and
synaptic pruning)
- White matter is ‘looking’ for new connections
The development of the (pre)frontal lobe (control of impulses, reasoning,
reflection, etc.)
- Matures last (compared to other brain regions)
- Particularly the white matter
- The volume of the gray matter decreases (pruning )
- Brain regions (grey matter) become smaller and more specialized →
needs less volume to perform at the highest level
- More space available for white matter (more contacts and synapses)
- Growth spurt at 3-4 years of age
- Another growth spurt at 8 years of age
- Maturation continues to 25-30 years of age
- Hence, young people struggle with impulse and behavioral control (e.g., they
do not abide by the corona rules)
- Most vulnerable to aging
- ‘Last in - first out’
- Executive functions related to the prefrontal cortex (e.g., planning, structuring
daily life, self-reflection, impulse control) are all affected by aging
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, - Cognitive reserve postpones age-related decline in cognitive functions
Environmental Influences on Brain Development
Brain plasticity
: the nervous system’s potential for physical or chemical change that
enhances its adaptability to environmental change and its ability to compensate for injury.
Environmental deprivation longer than 6 months has serious consequences for brain
development
- E.g., abnormal brain connectivity (i.e., white matter)
- Amblyopia : deficits of vision without obvious impairment of the eye
- Restricted visual experience as a baby/child → atypical functioning after the
period of deprivation
- Visual experience is necessary to validate functional connections in the brain
- Absence → loss of synapses (‘use it or lose it’)
- The earlier the deprivation takes place, the shorter the length of deprivation required
to produce effects and the more severe the effects
- If the environment is so arranged that the visual system is exposed to stimuli of one
type (e.g., vertical stripes), the cells in the system develop a preference for those
stimuli
- Preference for vertical stripes → no activity in response to horizontal stripes
Exposure to complex (rather than impoverished) environments:
- Increases brain size (most notably the neocortex)
- Greatest increase in the occipital lobe, which is very sensitive to complex
environments
- 70% of your brain is involved in visual processing
- Increases in density of glial cells, length of dendrites, density of s pines(the
location of most excitatory synapses), and size of synapses
- Young and adult brains respond differently to the same experience
- In young and old animals, the length of the dendrites increases
- As a result of an enriched environment
- However, the spine density (location of excitatory synapses in
particular)...
- Decreases in young animals
- Increases in old animals
- Can occur prenatally
- Mother placed in a complex environment → larger brain of
offspring → higher cognitive performance
-
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, According to Kennard’s principle, the impact of brain damage depends on:
- Function that is affected
- E.g., language may recover well in children
- Some areas recover better than others, even if the age at which the injury was
incurred is identical between patients
- Extent and location of the lesion
- Age at which the brain damage occurs (think of growth spurts). 3 critical ages:
- Before 1st year of life: brain damage has more impact compared to brain
damage at an older age
- 30% of growth spurts occur at this age
- Between 1st and 5th year of life: reorganization of functions is possible
- Largest chance of repair
- Older than 5 years of age: none of little sparing of function
Various factors can influence recovery from early cortical injury, including experience,
hormones, stress, drugs, and n eurotrophic factors1
- Functional recovery after early injury may result from modification of remaining
circuits, generation of new (abnormal circuits), or generation of neurons and glia
Language remains unaffected after LH-lesion at an early age
- This preservation is due to language capacities of the RH
- I.e., the RH will take over
- At the expense of visuospatial functions (crowdinge ffect
)
- Consequences of early RH-lesions remain present later in life and are comparable to
the consequences of lesions later in life
- I.e., the intact LH does not take over
- Whether the transfer of language is bilateral (both LH and RH contribute) or
complete (fully RH) depends on the area of the lesion to the LH
- Speech has a strong affinity for the LH and will not abandon it unless an entire
center is destroyed; even then, it might shift only partly to the other
hemisphere
- Plasticity depends on at least one intact hemisphere
- E.g., both LH and RH injured → no reorganization of language
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lass of nourishing compounds that support growth and differentiation in developing neurons and may act to keep certain
C
neurons alive in adulthood
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