Attention and Executive Function 1 Attention

Many cognitive capacities are inherently predicated on a fundamental ability to attend to the surrounding

Table I

General Intellectual Ability

Test name Description

The Wechsler Adult Intelligence Scale-III (WAIS-III) is composed of 13 individual subtests. Administration of all subtests generates three Intellectual Quotients (IQs): Full-Scale IQ, Verbal IQ and Performance IQ, and four different performance indices: Verbal Comprehension Index, Perceptual Organization Index, Working Memory Index, and Processing Speed Index.

Wechsler Intelligence Scales The Wechsler Abbreviated Scale of Intelligence (WASI) is designed to be a short and reliable measure of intelligence that produces VIQ, PIQ, and FSIQ scores that are similar to those obtained with the WAIS-III.

The Wechsler Intelligence Scale for Children (WISC-III) is used for testing children and adolescents ranging in age from 6 to 17.

The Wechsler Preschool and Primary Scale of Intelligence (WPPSI) is used for testing children ranging in age from 4 to 6.5 years.

American National Adult Reading Test The AmNART is a measure of recognition vocabulary requiring oral reading of 45

(AmNART) phonetically "irregular" words. It is used to estimate premorbid baseline intellectual ability in patients with known or suspected dementia. Similar measures include the NART, NART-Revised, and ANART. Errors consist of word mispronunciations.

Shipley Institute of Living Scale The Shipley ILS consists of a multiple-choice measure ofvocabulary (knowledge of synonyms)

and a measure of verbal reasoning (providing the missing member of an established logical pattern). The two components are scored together to estimate a WAIS-RFSIQ score. Errors consist of incorrect responses to the task involving choosing a synonym for the target word and providing no response or responding with an incorrect continuation of the logical pattern.

Raven's Standard and Colored Progressive These are standardized measures of nonverbal analogical reasoning widely used both within Matrices and outside the U.S. as a "culture fair'' measure of general intellectual ability. Both tests require the patient to demonstrate an understanding of the logic underlying visual patterns by selecting the missing component of the pattern from a series of choices. The Standard Matrices contain 60 black and white items ranging from simple to extremely difficult, while the Colored Matrices consist of 36 colored items that span a limited range of complexity. Errors consist of incorrect identification of the missing component of the visual pattern.

environment. For example, an individual cannot effectively name an object if the object is not first attended to and visually processed. Because attention is a prerequisite for other aspects ofcognitive function, disruption of attention can generally skew the results of a neuropsychological assessment. Early assessment of attention is vital for informing the scope of the examination and the analysis of test data (Table II).

Attention is a general term that encompasses a number of different component processes. Attention span refers to the number of unrelated ''bits'' of information that can be held on line at a given moment in time. Assessment of attention span is typically accomplished through the recall of progressively longer series of information bits, such as numbers (digit span) or spatial locations (spatial span). Sustained attention, also called vigilance, refers to the capacity to maintain active attention over time. The most common method of assessing vigilance utilizes a target detection paradigm. Here the patient is instructed to respond to an infrequently occurring target stimulus. For example, on a measure of auditory vigilance, the patient hears a series of letters of the alphabet and must signal by pressing a response key each time a particular target is read (see CPT, PASAT). Selective attention is similar to sustained attention but requires a response only to a particular class of stimuli, but not other stimuli. Set-shifting refers to the capacity to relinquish an existing procedural strategy in favor of a new response, based on recognition of a change in reward contingencies. It is typically measured with tasks requiring the patient to shift focus among stimulus features of test display (see Trailmaking A and B, Wisconsin Card Sorting Test, Luria Graphomotor Sequences). Resistance to interference, also called response inhibition, refers to the ability to sustain a given response, even in the face of a salient distraction designed to undermine the target response.

This is assessed with tasks requiring the patient to inhibit overlearned responses or other distractions that could undermine a desired response (see Stroop Interference Test, Trailmaking Test).

2. Executive Functioning

Executive functions require the capacity to process information in a planful, organized, and contextually appropriate manner. Formal tests of executive function assess a number of different capacities, including some functions mentioned earlier (set-shifting, overcoming interference, response inhibition), and also planning, perseverence, initiation, reasoning, and abstraction. Planning involves thinking several steps ahead of one's current circumstances for the purpose of informing and altering a course of action. Tests measuring planning ability often require a person to determine the correct series of steps needed to successfully reach a particular goal (see Tower of Hanoi, Tower of London). Perseverence is the ability to sustain a particular course of action, even in the absence of an external prompt. Measurement of perseverance often begins with both examiner and subject performing the same task, but involves the subject continuing the task even after the examiner has stopped (see Luria Motor Sequences, Verbal and Design Fluency). Initiation refers to the ability to spontaneously commence an action in the absence of a direct prompt from the external environment. This function is measured with the presentation of a task followed by a period of time during which the subject is expected to respond independently (see Verbal Fluency, Go-No-Go). Reasoning involves using a system of logic to solve a particular problem or task. This can be measured in a variety of ways, including the use of visual puzzles and verbal analogies (see Raven's Progressive Matrices, Shipley Institute of Living Scale-Abstraction, WAIS-III Comprehension). Abstraction is the ability to articulate shared attributes of dissimilar objects (see WAIS-III Similarities, Wisconsin Card Sorting Test) (Table II).

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