Cerebral Mechanisms of Learning Revealed by Functional Neuroimaging in Humans

Abstract

The functional neuroanatomy of cognitive processes in the human brain can be probed noninvasively at high spatial resolution with imaging techniques that record changes in regional cerebral blood flow (rCBF) and blood oxygenation. Of the two main available methods, positron emission tomography (PET, for review see Cherry and Phelps, 1996) and functional magnetic resonance imaging (fMRI) (for review see Di Salle et al., 1999; Moonen and Bandettini, 1999), the latter is being increasingly used because of its higher spatial and temporal resolution, the possibility to analyse single subject data and to measure the same subject repeatedly, even, as in some learning experiments and in a study of the effects of inverting goggles (Linden et al., 1999a), every day. FMRI relies on the blood oxygenation level-dependent (BOLD) contrast mechanism, first reported by Ogawa et al. in 1990 (Ogawa et al. 1990a, 1990b; Ogawa and Lee 1990) and widely applied to generate functional maps of the human brain since the pioneering studies of 1992 (Ogawa et al. 1992; Kwong et al. 1992; Bandettini et al. 1992). We will briefly explain the physiological basis of the BOLD contrast and outline the history of the use of this source of information about local brain activity for investigating the mechanisms of human perception and cognition. We will discuss the limitations of BOLD-fMRI and how to overcome them by combining fMRI with other neurophysiological techniques (‘multimodal functional neuroimaging’). In the main part, we will review some recent fMRI studies of procedural and associative learning whereas a detailed discussion of the large number of functional imaging studies of motor sequence learning falls without the scope of this chapter.