Gerstmann's+Syndrome

When the more **posterior portions of the left hemisphere** are damaged, naming (anomia), object and finger identification (agnosia), arithmetical abilities (acalculia), and temporal-sequential control over the hands (apraxia) are frequently compromised. A variety of symptoms areassociated with left inferior parietal lobe damage, some of which occur as a related constellation of disturbances, i.e. finger agnosia, acalculia, agraphia, and left-right disorientation: Gerstmann's syndrome. Gerstmann's symptom complex is most often associated with lesions in the area of the supramarginal gyrus and superior parietal lobule. However, because this symptom complex does not always occur together, some authors have argued that Gerstmann's syndrome, per se, does not exist.
 * Finger Agnosia, Acalculi, Agraphia, Left-Right confusion the knowing hand**

It has been said that the parietal lobule is an organ of the hand. The hand appears to be more extensively represented than any other body part, parietal neurons are responsive to hand movements and manipulations, mediate and visually observe temporal-sequential hand movements, and become highly activated in response to objects which are within grasping distance. Indeed, given that the parietal lobe receives lower visual field input, the area in which the hands are most likely to be viewed, it is therefore highly sensitive to and concerned with the somesthetic as well as the visual guidance of hand (and lower extremity) movements.

It is also via the hand that the parietal lobe gathers information regarding various objects, i.e. stereognosis, and about the Self and the World, so that things and body parts come to be known, named, and identified. Ontogenetically, the hand is in fact primary in this regard. That is, the infant first uses the hand to grasp various objects so they may be placed in the mouth and orally explored. As the child develops, rather than mouthing, more reliance is placed solely on the hand (as well as the visual system) so that information may be gathered through touch, manipulation and visual inspection. As the child and it's brain matures, instead of predominantly touching, grasping, and holding, the fingers of the hand are used for pointing and then naming -hand activities that are most likely to be viewed (and later remembered) by the parietal lobe. It is these same fingers which are later used for counting and the development of temporal-sequential reasoning; i.e. the child learns to count on his or her fingers, then to count (or name) by pointing at objects in space.

In this regard, counting, naming, object identification, finger utilization, and hand control are ontogenetically linked and seem to rely on the same neural substrates for their expression; i.e. the **left inferior and superior parietal lobule**. In this regard, the parietal lobe, due to its control over the hand, and its chronic surveillance of the lower visual field, is therefore the unique recipient and observer of specialized hand-related activities and has thus become organized accordingly in regard to the guidance, as well as the learning and memory of hand and finger related activities. **Finger Agnosia** Acalculia (Including Number Agnosia, Alexia, Agraphia)

Right-Left Disorientation

Attention and Neglect (particularly left sided neglect), including secondary delusional denial, disconnection, confabulation, gap filling, delusional playmates, egocentric speech