Parietal lobe: touch and body position awareness
The parietal lobe, behind the central sulcus (the groove separating it from the frontal lobe), deals with touch from the skin and awareness of where the body parts are.
Remember
Difficulty recognising objects by touch and loss of limb position sense, with normal strength, point to the parietal lobe; the problems are on the side of the body opposite the damage.
The parietal lobe sits behind the frontal lobe, just behind the central sulcus (the groove separating the two). Sensation from the skin, such as touch, pressure and pain, relays through the thalamus (the brain's sensory relay station) to the post-central gyrus, a ridge of cortex just behind that groove. This is the primary somatosensory cortex, which receives sensory information from the skin and body.
The lobe also gives awareness of the body. This sense is called proprioception (position sense), meaning where your limbs are in space.
Because these inputs are sensory, damage to the post-central gyrus affects feeling rather than movement. Damage to the lobe on one side can cause difficulty recognising objects by touch with the eyes closed, called astereognosis, and a loss of awareness of the opposite limb's position, with normal strength. The pre-central gyrus, the motor (movement) strip, lies in front of the groove.
The dominant parietal lobe, which is the left one in most right-handed people, also works with the frontal lobe in calculation and writing. So right-sided loss of touch recognition together with calculation and writing problems fits damage to the left parietal lobe.
Key facts
- Where it sits
- just behind the central sulcus, the groove separating it from the frontal lobe.
- Sensory strip
- the post-central gyrus is the primary sensory cortex of the parietal lobe.
- Thalamus
- sensory inputs from the skin relay through it to the parietal lobe.
- Body awareness
- the parietal lobe tells you where your body parts are in space (proprioception).
- Damage
- can cause difficulty recognising objects by touch (astereognosis) and loss of position sense.
- Dominant side
- parts of the dominant parietal lobe support calculation and writing.
Exam traps
- The frontal lobe does not explain difficulty recognising objects by touch with normal strength, because it controls movement, planning and behaviour, whereas touch recognition is a sensory problem.
- Problems with touch and position sense do not point to the occipital lobe, because the occipital lobe processes vision.
- Forming new episodic memories (memories of personal events) is not a primary parietal function, because it depends on the hippocampus in the medial temporal lobe.
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