Luria: Parietal lobes and complex simultaneous spatial synthesis

c5 p. 147 Luria The Working Brain

Luria notes this part of the brain is entirely human. It maintains connections with the thalamus and is a supramodal analyser. This is known by electrical stimulation and lesion studies that show no modally specific effects.

Luria compares lesions to those of simultaenous agnosia with an inability to fit together individual elements into a whole, or convert presentation of consecutive elementsinto simultaneous perceptibility. However, in addition, they cannot find their bearings within a system of spatial coordinates especially being able to tell right and left.

Patients get lost, cannot find their bed, cannot tell time from hands of a clock without numbers, find their bearings on a map, tell east from west, reproduce the position of the hand. They cannot draw letters due to inability to retain the required spatial position of the lines of the letters. Patients may write/draw mirror images. Severest form manifests in inability to directly reproduce 3D structures. Less severe forms include inability to reproduce spatial forms from memory. Other tasks are mirror reversal tasks. Constructional apraxia can occur.

Luria states that classical Gerstmann's syndrome ( acalculia, right-left confusion, finger agnosia, central alexia) has deeper roots with more symptoms. Complex logico-grammatical structures may be poorly understood, particularly with embedded constructions, passive actors and objects or sentences with the requirement of understanding the grammatical or spatial relationships among multiple actors.

The syntagmas, or syntactic structures expressing logical relationships is a term credited to the Swedish linguist Svedelius (1897). Communications of relationships occurred late in the evolution of languages, within the previous hundred(s) of years with the aid of inflections, prepositions or word order. All coded logical not concrete relationships, for example, the attributive genitive, "the father's brother." Although others called the inability to understand these relationships "semantic aphasia," Luria considers it a problem of spatial structures transferred to a higher symbolic level and affecting language.

Luria attributes acalculia to the use of internal spatial schemes such as tables, which are dependent for simultaneous synthesis and spatial operations, such as columns, to do arithmetic operations, and the need for right-left orientation to place the remainders in the correct position. Patients are aware of their inability to do complex operations, but are otherwise "intact" for motive, and otherwise.