Topic 7: Parietal Lobes & Attention Flashcards
Anterior Parietal Lobe: Primary Somatosensory cortex
The anterior parietal lobe contains the primary somatosensory cortex, which is responsible for processing and interpreting sensory information related to touch, pressure, vibration, temperature, and pain sensations from all parts of the body. This area is located in the postcentral gyrus, which is situated just posterior to the central sulcus that separates the parietal lobe from the frontal lobe.
The primary somatosensory cortex is organized in a somatotopic manner, meaning that specific regions of the body are represented in distinct areas of the cortex. The somatotopic map of the primary somatosensory cortex is known as the homunculus, and it reflects the relative sensitivity and importance of different body parts in sensory processing.
Posterior Parietal Lobe: Association Cortex
- considered as an association cortex because it integrates information from different sensory modalities and plays a role in higher-order cognitive processes, such as attention, perception, memory, and decision-making.
- Involved in spatial processing, which includes perceiving and understanding spatial relationships between objects and the body.
- Contains subregions like the superior and inferior parietal lobules and intraparietal sulcus, which play different roles in spatial processing.
- Involved in planning and executing movements that require complex sensorimotor integration and visuospatial attention.
- Receives inputs from the primary motor cortex and sensory cortices to transform sensory information into motor commands and coordinate movements.
- Involved in higher-order cognitive functions like working memory, decision-making, and attentional control.
- Highly interconnected with other cortical regions like the prefrontal and temporal cortex.
- Lesions or damage to this area can cause deficits in spatial processing, motor planning and execution, and higher-order cognitive functions.
MPR – medial parietal region
- active during navigation – cognitive spatial mapping
- Works with other regions such as parahippocampal, hippocampal, and posterior cingulate (parietal-medial temporal pathway of dorsal stream)
Parietal Damage Symptoms
- High sensory thresholds
- Astereognosis
- Asomatognosia – loss of awareness of ownership of a body part (e.g., arm, leg)
- Dyscalculia/Acalculia
- Disturbed language function
Dyscalculia/Acalculia
Damage to the parietal lobe, particularly in the left hemisphere, can lead to deficits in mathematical abilities, including dyscalculia and acalculia.
- Angular gyrus damage
Dyscalculia and acalculia are both conditions that involve difficulties with mathematical calculations.
- Dyscalculia (disability but still can) refers to a developmental disorder that affects a person’s ability to learn and perform arithmetic operations.
- In contrast, acalculia (complete lack of ability) is an acquired condition resulting from brain damage, typically in the parietal lobe.
Astereognosis
Being able to identify something with touch, partial damage may result in this being compromised. (in A)
Asomatognosia
Loss of awareness of a body part (e.g., arm, leg)
- e.g., someone pranked him and placed a cadavar leg in his bed, but it was his own leg and he couldn’t believe it was his
Apraxia
Apraxia is a neurological condition characterized by difficulty with planning and executing voluntary movements, despite the absence of muscle weakness or sensory loss. It can result from damage to various regions of the brain, including the parietal lobe.
Parietal lobe damage can cause two main types of apraxia:
-Ideomotor apraxia: This involves difficulty with executing movements in response to verbal commands or symbolic gestures (such as waving goodbye). Patients with ideomotor apraxia may have trouble performing complex actions, such as brushing their teeth or using utensils, even though they understand what the actions entail.
- Ideational apraxia: This involves difficulty with planning and sequencing the steps of a complex motor task. Patients with ideational apraxia may be unable to perform tasks such as dressing or cooking, even though they can perform the individual movements required for those tasks.
Simultaneous Extinction
Simultaneous extinction is a neurological phenomenon in which a person fails to perceive a stimulus in one-half of their visual field when two stimuli are presented simultaneously, one in each visual field. For example, if a person with simultaneous extinction is presented with a red dot in their left visual field and a green dot in their right, they may only report seeing the green dot, not the red dot.
Simultaneous extinction is most commonly associated with damage to the parietal lobe, particularly the right parietal lobe.
Simultaneous Extinction is a classical clinical sign of hemineglect or contralateral neglect = when someone has damage to the right hemisphere parietal lobe, which results in the neglect of their left side of space.
- something novel can cue them to focus their attention to the left slightly.
- “extinction” = you can extinguish their attention to the left side by simultaneously pressing two similar objects to both the right and left sides of space.
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Posner’s Attention Switching Paradigm
The task involves presenting a stimulus at the center of a computer screen, followed by a cue indicating where the next target stimulus will appear (either to the left or right of the center). The participant’s task is to quickly and accurately detect the target stimulus when it appears.
- COVERT attention (not explicit to participate)
- valid cue vs. invalid (80-20%) (i.e., valid cue tells them correctly where the target will appear, and it helps them 80% of the time)
- longer reaction time for invalid cues because it requires a switch; they must disengage and reengage
- associated with pariteal, superior colliculus, and thalamus
- focuses on selection attention
By analyzing participants’ response times and accuracy during the task, researchers can gain insight into the underlying mechanisms of attention and cognitive control.
Recruitment of DLPFC in Divided Attention
In divided attention tasks, individuals are required to perform two or more tasks simultaneously, such as listening to a conversation while driving. The dorsolateral prefrontal cortex (DLPFC) is a brain region known to be involved in cognitive control, including attention and working memory, and has been shown to be recruited during divided attention tasks.
- how the frontal lobe becomes engaged during these tasks is shown in the image (in the dorsal stream)
- Bimodal passive attention: In this task, participants are presented with stimuli from two different modalities simultaneously (e.g. visual and auditory), but they are not told to attend to either. Shows activity in the DLPFC.
- Bimodal auditory selective attention: In this task, participants are presented with two different auditory stimuli simultaneously and are instructed to attend to one stimulus and ignore the other. Activation in Sensory cortex activation
AUDITORY AREAS but not DLPFC
-Bimodal visual selective attention: In this task, participants are presented with visual stimuli and auditory stimuli simultaneously and instructed to attend to the visual stimuli and ignore the other. There is no DLPFC activation, but there is visual sensory cortical areas that are active in processing the information and, therefore, active.
- Bimodal divided attention: In this task, participants are presented with stimuli from two different modalities simultaneously and are instructed to attend to both modalities and perform a task on each stimulus. We need to process auditory and visual; we see DLPFC engagement. Dividing attention requires a higher central executive area.
Prism Effect / Prism Adaptation
- Prism goggles shifted to the right by 10 degrees
- Adaptation to prisms involves other regions, such as the cerebellum and frontal lobe (attention engagement)
- cerebellum plays a role in readjusting motor programs, which also means it plays a role in allocating attention
- The belief here as to why prism goggle can help as a therapy for people with contralateral neglect it is because it is believed that they engage other regions of the brain that are still intact (e.g., the cerebellum)
why is it that when we get damage in the right hemisphere we get contralateral neglect, but not when we have damage in the left hemisphere?
The left hemisphere parietal lobe seems to have attentional representation for the right side of space (i.e., we have this contralateral representation somewhat. Therefore, it primarily has right representation)
- if you damage left hemi and its representation of the right side allocation of attention, the right hemisphere can compensate for that because it has bilateral representation.
The right hemisphere has this allocation for both sides of space (i.e., left and right - bilateral representation).
- if you damage the right hemisphere, the left hemisphere only has right contralateral representation and cannot make up for the loss of the right hemisphere (i.e., the left side of space)
Bisiach & Luzzatti (1978) Study
Two men in 70’s – stroke patients with hemineglect
Piazza del Duomo (Milan)
- Memory intact: we have shown this by changing their perspective and therefore changing their attention to the memory
- Left-side neglect: the attention in the memory displays a left-side neglect
- Not externally driven
- Attention may be required to recall things
- Attention & memory are intimately linked
Simultagnosia
Cannot recognize more than 1 object at a time; if you show someone one thing at a time, they can recognize it, but if you show two things at a time, they can only recognize or perceive one of the things at a time.
