3. Pure word deafness. Although the patient is able to hear and identify nonverbal sounds, there is loss of ability to discriminate speech sounds, that is, to comprehend spoken language. The patient’s speech may be paraphasic, presumably because of the inability to monitor his own speech. This defect has been attributed to a subcortical lesion of the left temporal lobe, spanning the Wernicke area and interrupting also those auditory fibers that cross in the corpus callosum from the opposite side. Thus, there is a failure to activate the left auditory language area (Wernicke area). Bilateral lesions of the auditory cortex have the same effect (see Chap. 22).
4. Furthermore, all of the syndromes that span the occipital and either parietal or temporal lobes are, in effect intrahemispheric disconnections in the stream of visual information as discussed earlier.
In the study of focal cerebral disease, there are two complementary approaches: the clinical-neurologic and the neuropsychologic. The first consists of the observation and recording of qualitative changes in behavior and performance and the identification of syndromes from which one may deduce the locus and nature of certain diseases. The second consists of recording a patient’s performance on a variety of psychologic tests that have been standardized in a large population of age-matched normal individuals. These tests provide data that can be graded and treated statistically. An example is the deterioration index, deduced from the difference in performance on subtest items of the Wechsler Adult Intelligence Scale that hold up well in cerebral diseases (vocabulary, information, picture completion, and object assembly) and those that undergo impairment (digit span, similarities, digit symbol, and block design). A criticism of this index and others is the implicit assumption that cerebrocortical activity is a unitary function. However, it cannot be denied that certain psychometric scales reveal disease in certain parts of the cerebrum more than in others. These tests allow comparison of the patient’s deficits from one point in the course of an illness to another. Walsh has listed the ones that he finds most valuable. In addition to the Wechsler Adult Intelligence Scale, Wechsler Memory Scale, and an aphasia screening test, he recommends the following for quantifying particular psychologic abilities and skills:
I. Frontal lobe disorders
A. Milan Sorting Test, Halstead Category Test, and Wisconsin Card-Sorting Test as tests of ability to abstract and shift paradigms
B. The Porteus Maze Test, Reitan Trail-Making Test, and the recognition of figures in the Figure of Rey as tests of planning, regulating, and checking programs of action
C. Benton’s Verbal Fluency Test for estimating verbal skill and verbal regulation of behavior
II. Temporal lobe disorders
A. Figure of Rey, Benton Visual Retention Test, Illinois Nonverbal Sequential Memory Test, Recurring Nonsense Figures of Kimura, and Facial Recognition Test as modality-specific memory tests
B. Milner’s Maze Learning Task and Lhermitte-Signoret amnesic syndrome tests for general retentive memory
C. Seashore Rhythm Test, Speech-Sound Perception Test from the Halstead-Reitan battery, Environmental Sounds Test, and Austin Meaningless Sounds Test as measures of auditory perception
III. Parietal lobe disorders
A. Figure of Rey, Wechsler Block Design and Object Assembly, Benton Figure Copying Test, Halstead-Reitan Tactual Performance Test, and Fairfield Block Substitution Test as tests of constructional praxis
B. Several mathematical and logicogrammatical tests as tests of spatial synthesis
C. Crossmodal association tests as tests of suprasensory integration
D. Benson-Barton Stick Test, Cattell’s Pool Reflection Test, and Money’s Road Map Test, as tests of spatial perception and memory
IV. Occipital lobe disorders
A. Color naming, color form association, and visual memory, as tests of visual perception; recognition of faces of prominent people, map drawing