Novelty seeking and harm avoidance personality traits correlate with cerebellar volume in healthy volunteers

For a long time it was widely thought that the role of cerebellum is restricted to motor coordination and control of well-learned motor sequences. Recently there has been, however, increasing evidence pointing to other roles that the cerebellum possibly plays. One line of investigation has pointed to involvement of the cerebellum in “purely cognitive” functions such as attention (as recently highlighted also in this blog), processing of musical features (Alluri et al. 2012), and tentative findings of emotional disturbances in patients with cerebellar lesions, especially when involving the posterior lobe, have suggested an even more extensive role for cerebellum in supporting human cognitive-affective functions (Schmahmann & Sherman 1998).

In their recent study, Laricchiuta et al. (2012) measured the cerebellar volumes of an extensive sample (N=125) of healthy volunteers using magnetic resonance imaging. The same subjects were assessed with a comprehensive personality inventory (the Temperament and Character Inventory developed by Cloninger). Temperamental traits (that are assumed to be relatively stable over time and to a large extent genetically/biologically determined) were derived from the inventory, including novelty seeking, harm avoidance, reward dependence, and persistence. Notably, the authors observed that novelty-seeking scores were positively correlated, and harm-avoidance scores were negatively correlated, with cerebellar volumes.

These highly interesting findings add to the growing pool of evidence indicating that the role of cerebellum is much more extensive than what was for a long time assumed in cognitive neuroscience / neurology. While the involvement of cerebellum in cognitive processing has been widely demonstrated, studies on the role played by cerebellum in affective regulation and motivational-goal directed behavior, functions that are closely associated with novelty seeking and harm avoidance personality traits, have been more scarce. The findings of Laricchiuta et al. (2012) provide an important demonstration of an association between the novelty seeking and harm avoidance personality features and cerebellar structures, and pave way for further studies on the role of cerebellum in affective-cognitive regulation of behavior.

References:

Alluri V, Toiviainen P, Jaaskelainen IP, Glerean E, Sams M, Brattico E. Large­scale brain networks emerge from dynamic processing of musical timbre, key and rhythm. Neuroimage (2012) 59: 3677-3689. http://dx.doi.org/10.1016/j.neuroimage.2011.11.019

Laricchiuta D, Petrosini L, Piras F, Macci E, Cutuli D, Chiapponi C, Cerasa A, Picerni E, Caltagirone C, Girardi P, Tamorri SF, Spalletta G. Linking novelty seeking and harm avoidance personality traits to cerebellar volumes. Human Brain Mapping (2012) e-publication ahead of print. http://dx.doi.org/ 10.1002/hbm.22174

Schmahmann JD, Sherman JC. The cerebellar cognitive affective syndrome. Brain (1998) 121: 561–579. http://dx.doi.org/10.1093/brain/121.4.561

Acclimation to hypoxia protects brain tissue against the effects of a stroke

Stroke refers to ischemic conditions where blood flow to brain tissue is significantly reduced (typically when a clot blocks one of the arteries) causing lack of oxygen that results in destruction of brain tissue. Stroke currently constitutes one of the most severe medical problems, with one-third of deaths in Western societies being caused by stroke. Measures have been targeted to preventing / reducing the number of strokes (e.g., providing public information on factors elevating the risk for stroke and medically intervening when high blood pressure is detected), development of treatments that reduce brain damage caused by strokes (e.g., administration of clot-dissolving agents within three hours from the occurrence of a stroke), and rehabilitation methods. In addition to these, there is also research on ways to mitigate the damaging effects of stroke/ischemia.

In their recent study, Dunn et al. (2012) tested whether exposing experimental animals to hypoxia (i.e., keeping the experimental animals in chambers with half of the normal atmospheric pressure) over longer periods of time (in their study three weeks) reduces the effects of an experimentally induced stroke (occlusion of middle cerebral artery for 60 minutes). The authors note that hypoxia acclimation has been previously shown to induce changes that improve the capacity of tissue to survive low oxygen conditions, including increased capacity to supply oxygen (i.e., higher proportion of red blood cells and higher vascular density), more robust removal of end-products, and anaerobic energy production. In accordance with previous findings, they observed increased oxygen carrying capacity (increased hematocrit, capillary density, and tissue oxygen content) in the experimental animals that had been acclimated to hypoxic conditions. Notably, the animals that had been acclimated showed over 50% reduction in the extent of a lesion caused by the experimentally induced stroke, showed reduced inflammatory response, and less severe behaviorally measured dysfunction than control animals.

The authors suggest that increased oxygen levels and increased capillary density explain the beneficial effects of hypoxia acclimation, and point to possibilities for development of targeted treatments (that increase stroke-resistance via similar mechanisms as hypoxia acclimation) especially for high-risk patients such as those who have already suffered a transient ischemic attack which is a severe warning signal. These results are highly interesting and pave way for clinical research on additional measures to reduce the devastating consequences of stroke.

Reference: Dunn JF, Wu Y, Zhao Z, Srinivasan S, Natah SS. Training the brain to survive stroke. PLoS ONE (2012) 7: e45108. http://dx.doi.org/10.1371/journal.pone.0045108

Combat stress produces partially persistent changes to midbrain-prefrontal cortical circuitry and cognition

While acute short-lasting stress can be beneficial, such as when pushing to meet an important and potentially rewarding deadline at work, prolonged strong stress is known to cause cognitive impairments such as memory deficits. The precise nature and loci of anatomical and functional alterations due to chronic stress, and the extent to which they are (ir)reversible, constitutes an important topic in cognitive neuroscience that is being increasingly investigated.

In their recent follow-up study, van Wingen et al. (2012) investigated 33 healthy soldiers, using neuropsychological tests as well as functional and diffusion magnetic resonance imaging, first before a four-month combat-zone deployment to Afghanistan as a part of the North Atlantic Treaty Organization International Security Assistance Force peacekeeping operation. Then, follow-up studies were conducted 1.5 months (short-term) and 1.6 years (long-term) after the deployment. As a control group, they investigated 26 healthy soldiers who were not deployed at similar time intervals. During deployment, the combat group was exposed to typical combat zone stressors, such as armed combat, combat patrols, exposure to enemy fire, as well as risk of exposure to improvised explosive devices.

At the 1.5-month short-term follow up, midbrain activity was reduced in the combat group, including area containing substantia nigra. Functional connectivity between the midbrain area and lateral prefrontal cortex was also weakened. Combat stress further reduced fractional anisotropy and increased mean diffusivity in the midbrain areas, suggesting weakening of anatomical connectivity. Notably, these measures correlated with reduced performance in a sustained attention task. At the time of the long-term 1.6-year follow-up, the other deficits had normalized, but the reduced functional connectivity between the midbrain and prefrontal cortical areas persisted. The authors conclude that these persistent changes may increase the vulnerability to subsequent stressors and promote later development of difficulties with cognitive, social, and occupational functioning. More generally, these findings also provide important information about neurocognitive deficits that may develop when an individual is exposed to severe chronic stress in other types of context.

Reference: van Wingen GA, Geuzed E, Caan MWA, Kozicza T, Olabarriagah SD, Denysb D, Vermettend E, Fernándeza G. Persistent and reversible consequences of combat stress on the mesofrontal circuit and cognition. Proc Natl Acad Sci USA (2012) advance online publication. http://dx.doi.org/10.1073/pnas.1206330109