Naturalistic action impairment in closed head injury.

Abstract

The authors sought to determine whether errors of action committed by patients with closed head injury (CHI) would conform to predictions derived from frontal lobe theories. In Study 1, 30 CHI patients and 18 normal controls performed routine activities, such as wrapping a present, under conditions of graded complexity. CHI patients committed more errors even on the simplest condition; but, except for a higher proportion of omitted actions, their error profile was very similar to that of controls. Study 2 involved a subset of patients whose performance in Study 1 was within normal limits. When these high functioning patients were asked to perform the routine tasks under still more taxing conditions, they, too, committed errors in excess of the control group. Accounts based on frontal mechanisms have a difficult time explaining the overall pattern of findings. An alternative based on limited-capacity resources is suggested.

Event perception: A mind-brain perspective.

“…In this study, patients with frontal lesions who had difficulty performing sequentially structured activities also performed poorly at judgments about event structure including the script-listing task described previously. However, it is important to note that the question of whether action disorganization is the result of specific damage to event representations in PFC remains a matter of debate (Schwartz, et al, 1998).…”

Error detection and correction patterns in dementia: A breakdown of error monitoring processes and their neuropsychological correlates

“…The NAT manual describes a reliable and extensive coding system for classifying errors (comprehensive error score; CES; (Schwartz et al, 2003;Schwartz et al, 1998). According to the CES, an error is coded when a task step is performed incorrectly (i.e., sequence error, substitution, etc.…”

“…It is important to note that failure to complete large segments of the tasks does not necessarily lead to a reduction in overall error rate; for example, if a participant fails to make toast, he0she is assigned 4 omissions for the following steps: turn toaster on, toast bread, apply butter, apply jelly. The reader should refer to the NAT manual and prior publications for more details on the CES procedures (Giovannetti et al, 2002b;Schwartz et al, 1998;Schwartz et al, 2003).…”

Representing task context: proposals based on a connectionist model of action

“…Some of these pertain to the model's ability to capture particular behavioral phenomena. Specifically, the model produced at least one type of error (recurrent perseveration) not observed in the simulations of Cooper and Shallice (2000); it reproduced a correlation between error rate and the distribution of error types reported by Schwartz et al (1998), another effect not captured by Cooper and Shallice (2000); and, again unlike that earlier study, the Botvinick & Plaut (2002) model displayed a smooth variation in behavioral fragmentation with damage, a feature of ADS. Botvinick & Plaut (2002) also discuss several other advantages of the model over traditional accounts, including its reliance on learning instead of extensive ''hand wiring,'' its avoidance of the inflexible, ad hoc sequencing mechanisms typically incorporated into traditional models, and its relative strength in dealing with context-sensitive behavior.…”

“…With increasingly severe disruption to the model's context representations, the model's behavior became gradually more fragmented, coming to resemble the performance of ADS patients as characterized in recent empirical studies (e.g. Humphreys & Forde, 1999;Schwartz et al, 1998). Botvinick & Plaut (2002) point to a number of apparent advantages of the model over traditional accounts of routine sequential action.…”