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Localization of brain functions in humans has become much easier with the advent of brain imaging methods (PET and fMRI). This research has confirmed that areas in the PFC are involved in working memory functions. During the 1990s much debate has centered on the different functions of the ventrolateral (i.e., lower areas) and the dorsolateral (higher) areas of the PFC. A human lesion study provides additional evidence for the role of the dorsolateral prefrontal cortex in working memory. One view was that the dorsolateral areas are responsible for spatial working memory and the ventrolateral areas for non-spatial working memory. Another view proposed a functional distinction, arguing that ventrolateral areas are mostly involved in pure maintenance of information, whereas dorsolateral areas are more involved in tasks requiring some processing of the memorized material. The debate is not entirely resolved but most of the evidence supports the functional distinction.

Localization of brain functions in humans has become much easier with the advent of brain imaging methods (PET and fMRI). This research has confirmed that areas in the PFC are involved in working memory functions. During the 1990s much debate has centered on the different functions of the ventrolateral (i.e., lower areas) and the dorsolateral (higher) areas of the PFC. A human lesion study provides additional evidence for the role of the dorsolateral prefrontal cortex in working memory. One view was that the dorsolateral areas are responsible for spatial working memory and the ventrolateral areas for non-spatial working memory. Another view proposed a functional distinction, arguing that ventrolateral areas are mostly involved in pure maintenance of information, whereas dorsolateral areas are more involved in tasks requiring some processing of the memorized material. The debate is not entirely resolved but most of the evidence supports the functional distinction.

Brain imaging has revealed that working memory functions are not limited to the PFC. A review of numerous studies<ref>{{Cite journal|vauthors=Smith EE, Jonides J |title=Storage and executive processes in the frontal lobes |journal=Science |volume=283 |issue=5408 |pages=1657–61 |date=March 1999 |pmid=10073923 |doi=10.1126/science.283.5408.1657|citeseerx=10.1.1.207.8961 }}</ref> shows areas of activation during working memory tasks scattered over a large part of the cortex. There is a tendency for spatial tasks to recruit more right-hemisphere areas, and for verbal and object working memory to recruit more left-hemisphere areas. The activation during verbal working memory tasks can be broken down into one component reflecting maintenance, in the left posterior parietal cortex, and a component reflecting subvocal rehearsal, in the left frontal cortex (Broca's area, known to be involved in speech production).<ref>{{Cite journal|author=Smith, E. E.|author2=Jonides, J.|author3=Marshuetz, C.|author4=Koeppe, R. A.|title=Components of verbal working memory: evidence from neuroimaging |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=95 |issue=3 |pages=876–82 |date=February 1998 |pmid=9448254 |pmc=33811 |doi=10.1073/pnas.95.3.876|bibcode=1998PNAS...95..876S }}</ref>

Brain imaging has revealed that working memory functions are not limited to the PFC. A review of numerous studies<ref>{{Cite journal|vauthors=Smith EE, Jonides J |title=Storage and executive processes in the frontal lobes |journal=Science |volume=283 |issue=5408 |pages=1657–61 |date=March 1999 |pmid=10073923 |doi=10.1126/science.283.5408.1657|citeseerx=10.1.1.207.8961 }}</ref> shows areas of activation during working memory tasks scattered over a large part of the cortex. There is a tendency for spatial tasks to recruit more right-hemisphere areas, and for verbal and object working memory to recruit more left-hemisphere areas. The activation during verbal working memory tasks can be broken down into one component reflecting maintenance, in the left posterior parietal cortex, and a component reflecting subvocal rehearsal, in the left frontal cortex (Broca's area, known to be involved in speech production).<ref>{{Cite journal|author=Smith, E. E.|author2=Jonides, J.|author3=Marshuetz, C.|author4=Koeppe, R. A.|title=Components of verbal working memory: evidence from neuroimaging |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=95 |issue=3 |pages=876–82 |date=February 1998 |pmid=9448254 |pmc=33811 |doi=10.1073/pnas.95.3.876|bibcode=1998PNAS...95..876S }}</ref>

Brain imaging has revealed that working memory functions are not limited to the PFC. A review of numerous studies shows areas of activation during working memory tasks scattered over a large part of the cortex. There is a tendency for spatial tasks to recruit more right-hemisphere areas, and for verbal and object working memory to recruit more left-hemisphere areas. The activation during verbal working memory tasks can be broken down into one component reflecting maintenance, in the left posterior parietal cortex, and a component reflecting subvocal rehearsal, in the left frontal cortex (Broca's area, known to be involved in speech production).

Brain imaging has revealed that working memory functions are not limited to the PFC. A review of numerous studies shows areas of activation during working memory tasks scattered over a large part of the cortex. There is a tendency for spatial tasks to recruit more right-hemisphere areas, and for verbal and object working memory to recruit more left-hemisphere areas. The activation during verbal working memory tasks can be broken down into one component reflecting maintenance, in the left posterior parietal cortex, and a component reflecting subvocal rehearsal, in the left frontal cortex (Broca's area, known to be involved in speech production).