Authors:

OWEN, A.M

Reference:

Year of publication:

2005

CBU number:

5380

Abstract:

The frontal lobes have long been thought to play an important role in planning behaviour; For example, Harlow (1868), argued that frontal-lobe lesions in humans result in a loss of ‘planning skill’, whilst much later, Bianchi (1922), described a loss in the ability to ‘coordinate the different elements of a complex activity’ in monkeys with large frontal lesions. More contemporary accounts have characterised the role of the frontal cortex in planning behaviour using similarly descriptive, terms; e.g. ‘as a general system for sequencing or guiding behaviour towards the attainment of an immediate or distant goal (Jouandet and Gazzaniga, 1979), or as crucial for the ‘planning of future actions’ (for review, see Shallice, 1988). Until recently, however, the assumed relationship between cognitive planning and the frontal lobes lacked solid empirical support and was based largely on anecdotal reports of disorganized behaviour in patients with relatively non-specific brain injury, or on the behaviour of monkeys with large excisions of the frontal cortex. Moreover, planning difficulties are not unique to patients with circumscribed frontal-lobe damage. For example, ‘frontal-like’ planning deficits have been described in patients with mild Parkinson’s disease (Morris et al., 1988; Owen et al., 1992; 1995a; 1998), and other basal-ganglia disorders, suggesting that an equivalence between the prefrontal cortex and planning function cannot be assumed. In recent years, a substantial number of studies have elected to use versions of the Tower of London task to investigate cognitive planning in humans (e.g. Baker et al., 1996; Dagher et al.,, 1999; 2001; Hodgson et al., 2000; 2002; Morris et al., 1988; 1993; Owen et al., 1990; 1992; 1995a; 1996a; 1998; Rowe et al., 2001; Shallice, 1982). As a direct result, a wealth of new evidence has accumulated, both supporting a role for the frontal-lobe in planning behaviour and providing more precise psychological information about the nature of that role. This chapter will review that evidence and in doing so, attempt to summarise the findings in terms of their contribution to current understanding about the cognitive and neuroanatomical bases of complex planning behaviour.