Editing Neuroscience and intelligence (section)

===Neural efficiency===

The neural efficiency hypothesis postulates that more intelligent individuals display less activation in the brain during cognitive tasks, as measured by Glucose metabolism.<ref name=Haier1988 /> A small sample of participants (N=8) displayed negative correlations between intelligence and absolute regional metabolic rates ranging from -0.48 to -0.84, as measured by PET scans, indicating that brighter individuals were more effective processors of information, as they use less energy.<ref name=Haier1988 /> According to an extensive review by Neubauer & Fink<ref name="Neubauer2009">Neubauer, A. C., & Fink, A. (2009). Intelligence and neural efficiency. ''Neuroscience & Biobehavioral Review''s, 33(7), 1004-1023.</ref> a large number of studies (N=27) have confirmed this finding using methods such as PET scans,<ref name="Andreasen1995">{{cite journal | last1 = Andreasen | first1 = N.C. | last2 = O'Leary | first2 = D.S. | last3 = Arndt | first3 = S. | last4 = Cizadlo | first4 = T. | last5 = Rezai | first5 = K. | last6 = Watkins | first6 = G.L. | last7 = Boles Ponto | first7 = L.L. | last8 = Hichwa | first8 = R.D. | year = 1995 | title = PET studies of memory: novel and practiced free recall of complex narratives | journal = NeuroImage | volume = 2 | issue = 4| pages = 284–295 | doi=10.1006/nimg.1995.1036| pmid = 9343613 | s2cid = 19745366 }}</ref> EEG<ref name="Doppelmayer1998">{{cite journal | last1 = Doppelmayr | first1 = M. | last2 = Klimesch | first2 = W. | last3 = Schwaiger | first3 = J. | last4 = Auinger | first4 = P. | last5 = Winkler | first5 = T. | year = 1998 | title = Theta synchronization in the human EEG and episodic retrieval | journal = Neurosci. Lett. | volume = 257 | issue = 1| pages = 41–44 | doi=10.1016/s0304-3940(98)00805-2| pmid = 9857961 | s2cid = 11307011 }}</ref> and fMRI.<ref name="Rypma1999">{{cite journal | last1 = Rypma | first1 = B. | last2 = D'Esposito | first2 = M. | year = 1999 | title = The roles of prefrontal brain regions in components of working memory: effects of memory load and individual differences | journal = PNAS | volume = 96 | issue = 11| pages = 6558–6563 | doi=10.1073/pnas.96.11.6558| pmid = 10339627 | pmc = 26921 | bibcode = 1999PNAS...96.6558R | doi-access = free }}</ref>

fMRI and EEG studies have revealed that task difficulty is an important factor affecting neural efficiency.<ref name=Neubauer2009 /> More intelligent individuals display neural efficiency only when faced with tasks of subjectively easy to moderate difficulty, while no neural efficiency can be found during difficult tasks.<ref name="Neubauer1999">Neubauer, A.C., Sange, G., Pfurtscheller, G., 1999. Psychometric intelligence and event-related desynchronisation during performance of a letter matching task. In: Pfurtscheller, G., Lopes da Silva, F.H. (Eds.), Event-Related Desynchronization (ERD) and Related Oscillatory EEG-Phenomena of the Awake Brain. Elsevier, Amsterdam, pp. 219–231.</ref> In fact, more able individuals appear to invest more cortical resources in tasks of high difficulty.<ref name=Neubauer2009 /> This appears to be especially true for the Prefrontal Cortex, as individuals with higher intelligence displayed increased activation of this area during difficult tasks compared to individuals with lower intelligence.<ref name="Callicott1999">{{cite journal | last1 = Callicott | first1 = J. H. | last2 = Mattay | first2 = V. S. | last3 = Bertolino | first3 = A. | last4 = Finn | first4 = K. | last5 = Coppola | first5 = R. | last6 = Frank | first6 = J. A. | year = 1999 | title = Physiological characteristics of capacity constraints in working memory as revealed by functional MRI | journal = Cerebral Cortex | volume = 9 | issue = 1| pages = 20–26 | doi=10.1093/cercor/9.1.20| pmid = 10022492 | doi-access = free }}</ref><ref name="Rympa2006">Rypma, B., Berger, J. S., Prabhakaran, V., Bly, B. M., Kimberg, D. Y., &
Biswal, B. B. (2006). Neural correlates of cognitive efficiency. NeuroImage,
33(3), 969 –979.</ref> It has been proposed that the main reason for the neural efficiency phenomenon could be that individuals with high intelligence are better at blocking out interfering information than individuals with low intelligence.<ref name="Gray2003">{{cite journal | last1 = Gray | first1 = J. R. | last2 = Chabris | first2 = C. F. | last3 = Braver | first3 = T. S. | year = 2003 | title = Neural mechanisms of general fluid intelligence | journal = Nature Neuroscience | volume = 6 | issue = 3| pages = 316–322 | doi=10.1038/nn1014 | pmid=12592404| s2cid = 10492067 }}</ref>