This is a brief overview of the literature on Brodmann Area 9 (BA9) which overlaps with the Dorsolateral Prefrontal Cortex (which also includes BA10-12 and BA 45-47 although there is some variation according to definition). Medline was searched using the term ‘Brodmann Area 9’ and retrieved articles were scanned for relevance. From the retrieved papers there was a demarcation between physiological and pathological studies with the majority of studies falling into the latter category. In terms of physiological studies predicting how narratives progressed was assumed by the researchers in one study to result from ‘strategic inference’ and they correlated an increased haemodynamic response in the Left BA9 region. Von Economo Neurons were identified in BA9 in one small immunohistochemical study. Comprehension of idioms was associated with activity in BA9 in one study (freely available here). NK1 and NK3 receptors were identified in BA9 cell layers in one study. BA9 activation was increased in a semantic categorisation task in one fMRI study. A combined PET and Magnetoencephalography study identified BA9 as being associated with motor readiness in this study. A ‘Theory of Mind’ task was associated with left sided BA9 activation in one study. 488 unique proteins were identified in a shotgun mass spectrometry proteome study of BA9.
In terms of pathological studies there were a large number of conditions associated with BA9 including Bipolar Disorder, Schizophrenia, Vascular Dementia, Parkinson’s Disease and Congenital Scoliosis. In an analysis of fMRI studies there was found to be an association between BA9 and depressive disorder although the finer details differed between studies. Epidural Cortical Stimulation of left BA9 was associated with clinical improvement in treatment resistant depression in this study (n=12). Major Depressive Disorder was associated with significantly lower neuropeptide somatostatin in the Dorsolateral Prefrontal Cortex in comparison with a control group and a group with Bipolar Disorder. In a small post-mortem study (n=20) pro-apoptotic factors were found to be significantly increased in BA9 in the brains of people with Bipolar Disorder compared to a control group with the researchers speculating on a degenerative association (freely available here).In a study in which the researchers sampled grey matter lipid levels in the BA9 region and found significant difference in their sample of people with Bipolar Disorder and Schizophrenia in comparison with a control group. There was found to be a significant reduction in Oligodendrocytes layer VI of BA9 in people with Schizophrenia, Major Depressive Disorder and Bipolar Disorder in one study. Neuropeptide Y mRNA expression was decreased in people with Bipolar Disorder in one study compared to a control group.
In a study of people with Schizophrenia, performance on the Wisconsin Card Sorting Test was lower in a low performing on an eye tracking task compared to a high performing group. Interestingly there was no associated change in regional Cerebral Blood Flow (rCBF) in the DLPFC using SPECT. Postsynaptic density protein 95 (PSD95) mRNA was reduced in BA9 in people with Schizophrenia compared to a control group in one study. Pyramidal cell density in BA9 were asymmetrical and reversed in a comparison of controls with people with schizophrenia (freely available here). Patients with schizophrenia showed significantly different signal dynamics between the Right Amygdala and BA9 compared to a control group in this study. Minor changes in BA9 were found in a small study comparing people with Schizophrenia with a control group. One study found decreased Glutamic Acid Decarboxylase mRNA expression in BA9 in Parkinson’s Disease in a small post-mortem study comparing people with Parkinson’s Disease with a control group. Levels of monocyte chemo-attractant protein were found to be significantly reduced in people with Vascular Dementia and Mixed Dementia compared to a control group in this small study. Loss of vesicular glutamate transporters VGLUT1 and VGLUT2 in BA9 was associated with cognitive decline in Alzheimer’s Disease in one study. Cognitively normal people over the age of 65 displayed no evidence of loss of synaptic volume density in BA9 lamina III and V in one study. Somatostatin deficit were only identified in BA9 and not other areas in Alzheimer’s Disease in this study. Loss of somatostatin immunoreactivity was found in BA9 in people with Alzheimer’s Disease carrying the APOE4 allele compared to a group that did not carry the allele and the researchers suggest that this may be a marker of somatostatinergic dysfunction. There were significant differences between people with Alzheimer’s Disease and controls in fatty acid levels in BA9 in this study.
In a comparison of proteomes in BA9 in controls and people with alcohol misuse there were a number of differently expressed proteins in the latter group including Thiamine-dependent enzymes transketolase and pyruvate dehydrogenase (E1β ubunit). In an EEG study there was a significant difference in Medial Prefrontal Cortex P300 responses to food between groups categorised according to BMI. 5-HT2A binding potential in the BA9 was associated with aggressive behaviour in a small PET case-control study (freely available here). In an fMRI study insomnia (freely available here) was associated with hypoactivation of BA9 with activity increasing after sleep therapy. In a small case-control study glucose hypometabolism was found in people with congenital scoliosis compared to a control group (freely available here).
Appendix – Articles Reviewed in relation to Brodmann Areas or other Structures
Brodmann Area 1 – Somatosensory Cortex
Brodmann Area 2 – The Primary Motor Cortex
Brodmann Area 6 (Agranular Frontal Area 6)
Brodmann Areas 5 and 7 (Somatosensory Association Cortex)
Brodmann Area 8
Brodmann Areas 13 and 14 (Insular Cortex)
Brodmann Area 15 (Anterior Temporal Lobe – Controversial Area in Humans)
Brodmann Area 25 – Anterior Cingulate Cortex
Brodmann Area 27 (Piriform Cortex)
Brodmann Area 28 (Entorhinal Cortex)
Brodmann Areas 45, 46, 47 (Inferior Frontal Gyrus)
Medial Temporal Lobe
Miscellaneous Subcortical Structures
Generic Articles Relating to Localisation
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