Frontal lobes and human memory | Brain | Oxford Academic
loss of the normal relationships between different domains of executive function temporal lobe structures in executive function and the results of those studies have schizophrenia (Robbins, , ; Pantelis and Brewer,. , ). The new functional neuroimaging techniques, PET and functional MRI (fMRI), offer of the frontal cortex will ultimately depend on a fuller cognitive psychological AFC = anterior frontal cortex;, DLFC = dorsolateral frontal cortex; , ERP = event-related potential;, FC = frontal cortex;, fMRI = functional MRI; Brewer et al. See other articles in PMC that cite the published article. the laboratory tasks, and non-cognitive factors such as motivation may play a role. elicited the greatest and most consistent age-related differences in PM Support for a selective decline in frontal lobe function has come from a variety of sources.
Also PET has shown decreased glucose utilization in the medial—frontal regions of neurologically unaffected alcoholic patients Samson et al. The rate of response in the orbitofrontal cortex was significantly correlated with cerebellar metabolism at baseline. Results suggest that chronic alcohol intakes result in impaired function of cerebral tissue in the medial frontal region, affecting tissue metabolic rates and the behaviour correlates of these rates.
Furthermore, Adams et al. They found that impaired performance on the summary subtest of the HCT was correlated with local cerebral metabolic rate for glucose in all three frontal subdivisions cingulate, dorsolateral and orbitomedialwhereas the impairment in the summary WCST measure of categories was correlated only with local cerebral metabolic rate in the cingulate region. They suggested that these abnormalities in functioning of the subdivisions of the frontal lobe might contribute to different aspects of the behavioural impairment seen in older alcoholic patients.
Additionally, Adams et al. Forty-eight subjects, who had histories of severe chronic alcohol dependence, were divided into two groups: No differences were found between groups on either neuropsychological or neuroimaging tests. These results suggest that a family history of alcoholism does not moderate the damaging effects of severe chronic alcoholism on the functioning of the medial frontal lobe.
However, Harden and Pihlin assessing the profile of cognitive dysfunction drawn from neuropsychological tests designed to assess the functional integrity of the frontal lobes, observed a relationship between high-risk status in sons of male multigenerational alcoholics and their performance on frontal lobe tests.
Nevertheless the sample size was small 14 boys with, and 14 without, a positive family history of alcoholism. Other recent studies Deckel et al. Initially, global CBF was measured by determining the arteriovenous difference of the inert gas nitrous oxide.
Later, the external detection of flow markers labelled with single photon emitting isotopes allowed more regional measurement of CBF. SPECT essentially measures regional cerebral blood flow rCBF by following the transport of a single photon-emitting radioisotope tracer to the brain and measuring the resultant activity with detectors. Early studies generally showed reduction in CBF in chronic alcoholics and patients with Korsakoff's syndrome Meyer et al.
However, several studies suffered from serious shortcomings: In several interesting reports, CBF was measured by the non-invasive Xe inhalation method in volunteers recruited for a study of the effects of ageing, risks factors for cerebrovascular disease and dementia on CBF.
Gray matter CBF significantly inversely correlated with the average alcohol consumption over previous years, which ranged from nil to heavy social drinking. This was regardless of whether or not risk factors for cerebrovascular disease were present Roger et al. Flow measurements were reported in patients with Wernicke—Korsakoff syndrome Meyer et al.Craft Brewing in the Alaskan Wilderness: Craftwerk with 49th State Brewing Company
In chronic alcoholic subjects, values for gray matter flow were normal. Patients were restudied after several weeks of abstinence and thiamine treatment in the case of the Wernicke—Korsakoff patients. In the compliant subgroups, flow values increased to normal in both sets of patients. A French study looked at the relation between hepatic pathology and CBF in chronic alcoholics.
Reductions in flow were found to correlate with the severity of the hepatic histological abnormalities, though not with the results of the usual biochemical liver function tests Valmier et al.
These findings are in line with one of the first CBF studies in alcoholism where the results showed the greatest flow reduction in patients with cirrhosis Shimojo et al. Additionally, later pathological studies supported the contribution of alcohol, thiamine deficiency and cirrhosis of the liver to cerebral cortical damage in alcoholics Harper and Kril, ; Kril, Berglund and Risberg made serial bilateral measurements of regional rCBF by the Xe inhalation method, during 13 withdrawal periods in 12 male alcoholics with pronounced physical dependence.
A significant global reduction of rCBF was found during the first two days of withdrawal. Results indicated that there were significantly reduced left frontal and right frontal, parietal and temporal rCBF values in the patients during alcohol withdrawal compared to those of their remitted state, which were not different from those in the control group.
They evaluated 40 asymptomatic chronic alcoholics and 20 age-matched controls. SPECT showed hypo-perfusion in the orbital and medial—frontal lobe regions and the medial diencephalic area.
This showed a return to normal perfusion in the frontal brain areas, but little improvement in the medial diencephalic region. However, it is difficult to generalize from only one case report.
Frontal lobe involvement in a task of time-based prospective memory
The authors found a significant reduction in regional cerebral blood flow rCBF measurements of the alcoholic patients. Low flow in frontal regions encountered in However, patients with antisocial personality exhibited more marked frontal hypo-perfusion. Meanwhile, Jagannathan et al. They studied the brain metabolic changes in 10 alcoholic patients in the frontal lobe, cerebellum, and thalamus regions. The results obtained were characterized by a reduced N-acetyl-aspartate NAA: These decreased ratios correspond to depleted concentration of metabolite levels.
Reduction of NAA is consistent with neuronal loss, whereas reduction in Cho suggests significant changes in the membrane lipids of alcoholics. Interestingly, Gansler et al. Results showed a positive relationship between perfusion levels in the left inferior frontal brain region and years of sobriety. Alcoholics with less than 4 years of sobriety had significantly reduced left inferior frontal perfusion, compared with both non-alcoholic controls and alcoholics having longer periods of sobriety.
The findings support the hypothesis that frontal brain abnormalities in alcoholics may subside with extended abstinence. Additionally, both electroencephalographic EEG and evoked potential studies support the presence of neurophysiological changes in brains of alcoholics, particularly in the frontal lobe Pribram and Luria, ; Begleiter et al. These studies led Begleiter et al. They speculated that these electrophysiological deficits might reflect the imminent onset of overt structural changes.
The microscopic picture was one of cell loss, architectural disruption of the cortical laminae, pigmentary degeneration and proliferation of glial elements. In his experience, this picture was sometimes accompanied by marked arteriosclerotic changes.
This description was supported by other authors Warner, ; Hecaen and Ajuriaguerra, ; Mancall, The picture of cortical atrophy, particularly involving the frontal lobes, may occur alone or in combination with other lesions.
Cortical atrophy has also been described in combination with degeneration of the corpus callosum in cases of Marchiafava—Bignami syndrome Jequier and Wildi, ; Delay et al. Finally, we confine our review to studies of groups of young, healthy individuals.
The nature of the contribution of the frontal lobe to memory is clouded by the division of the experimental literature into two broad fields: While there are good reasons for distinguishing between these two types of memory, it is also likely that considerable overlap exists between the frontally mediated processes involved in each.
Many imaging studies of encoding and retrieval in LTM, for example, are likely to entail maintaining and manipulating information in WM.
It is interesting, therefore, that similar FC dissociations of function have been proposed in both LTM and WM imaging studies, and yet these findings, with certain exceptions Wagner,are not often considered together. Nonetheless, a convenient way to introduce the evidence is to consider each field separately, before subsequently discussing how they may converge. We therefore address the patterns of memory-related FC activation in two stages.
Secondly, in the concluding section, we attempt a more general interpretation that extends to FC activations across the different domains. However, the term has different connotations in different fields.
In the animal literature, it is often used to describe the ability of an animal to remember a stimulus for a short period after it is removed in order to perform e.
Frontal lobe and cognitive development.
In the cognitive psychological literature, on the other hand, WM frequently refers to a mental workspace in which multiple sources of information are manipulated in order to perform complex problem-solving tasks. We begin by introducing the background to these two perspectives, before considering recent imaging studies that have attempted to synthesize ideas from these traditionally quite distinct fields of investigation. Perspectives from animal studies: These theories concentrate in particular on dissociations between ventral and dorsal regions of lateral FC.
According to the domain-specific theory, FC is the primary site of WM processes and different regions within FC process different types of information Goldman-Rakic, Specifically, VLFC is believed to be responsible for the maintenance of stimulus form object informationwhereas DLFC is believed to be responsible for the maintenance of stimulus location spatial information.
More specifically, Wilson and colleagues found that FC cells ventral to the principal sulcus code for object information during a delay, whereas frontal cells within and dorsal to the principal sulcus code for spatial information during a delay Wilson et al.
That is, there is no suggestion of specialization for different WM processes across FC, only specialization for the domains over which these processes operate. The alternative, process-specific theory proposes that the difference between VLFC and DLFC lies not in the type of material being maintained but in the type of processes operating on that material Petrides, This theory derives mainly from animal lesion data Petrides, and has been extended to human lesion data Petrides and Milner, ; Owen et al.
This information may have been perceived recently or retrieved from LTM. DLFC, however, supports more complex processes operating on information that is currently maintained in WM. These include processes such as monitoring and higher-level planning.
The process-specific distinction can be illustrated by comparing two types of WM task. This task requires maintenance only. This requires that the subject not only selects stimuli from a set maintained in WM but also updates and monitors the set of previous responses.
Consistent with this view, DLFC lesions in primates produce deficits on self-ordering tasks but not typically on delayed-matching tasks Petrides, Self-ordering deficits are also seen following frontal lesions in patients, which typically include DLFC Petrides and Milner, ; Owen et al.
Furthermore, a review by D'Esposito and Postle found no evidence that patients with DLFC lesions were impaired on simple verbal or spatial span tasks that require only maintenance of a stimulus on-line without any manipulation D'Esposito and Postle, Though often placed in opposition, the domain-specific and process-specific theories are not necessarily incompatible.
FC may be functionally dissociable according to both the type of material and the type of process. Moreover, the precise site of lesions in the primate DLFC e. Brodmann areas 9 or 46 can affect whether impairments are seen in simple spatial delayed response tasks or only in more complex situations, such as self-ordering tasks. Nonetheless, we will compare these two general theories for their ability to account for the human imaging data.
The data are introduced later, after considering an alternative perspective on WM deriving from the human psychological literature. Perspectives from human cognitive psychology: This model was developed to account for a range of different WM functions, from temporary maintenance of a single stimulus to the manipulation of multiple types of information.
An important distinction within the slave systems of the WM model is between passive storage and active rehearsal. The rapid decay of material in the phonological store can be offset, however, by subvocal rehearsal via the articulatory control process.
For the purpose of this review, we make a coarse distinction between imaging studies of WM that employ maintenance tasks and those that employ manipulation tasks. Maintenance refers to the process of keeping information in mind in the absence of an external stimulus and perhaps in the presence of distraction.
This would correspond to use of the slave systems of the WM model. Manipulation refers to the reorganization of the information that is being maintained, and would correspond to the use of the central executive in the WM model. We begin by considering maintenance tasks. Early imaging studies of such tasks have tended to support the neuropsychological evidence for a role of posterior regions in the passive storage of material and of posterior FC in the rehearsal of material.
Both have been lateralized to the left for verbal material and to the right for spatial material.
We then consider manipulation tasks. These have been the subject of more recent imaging studies which have focused on dissociations between VLFC and DLFC and are thus relevant to the domain-specific versus process-specific debate outlined above.
The goal of the subject is to decide whether or not the probe stimulus was one of the stimuli in the memory set. To isolate brain areas involved in maintenance from those involved in perceptual or motor components of the task, functional images obtained during the Sternberg task can be contrasted against those obtained in a control task in which the memory set and probe item are presented simultaneously, alleviating any memory requirement.
Frontal lobe and cognitive development.
Using a verbal Sternberg task in which the stimuli were letters Fig. Similar regions were implicated by Paulesu and colleagues when they compared two Sternberg tasks, one using letters and one using non-verbalizable symbols Fig.
This left hemisphere network of the VLFC, parietal and motor areas plus right cerebellum is a consistent finding in studies of maintenance in verbal WM Smith and Jonides, ; Henson et al. To distinguish the storage and rehearsal components of verbal WM, Paulesu and colleagues Paulesu et al. This comparison revealed left inferior parietal activation but no FC activation. Awh and colleagues compared a 2-back task in which a positive response is required whenever the current stimulus matches the stimulus presented two trials previously Fig.