How does childhood trauma affect the adult brain?
Negative childhood experiences and the adult brain's spontaneous activity
Posted October 1, 2015
Our brain is always there. From birth, and even prenatally, it is exposed to the environment. How does the brain react to that? The brain shows spontaneous or intrinsic activity that seems to remain independent of specific stimuli or tasks. At first glance one may assume that the spontaneous activity isolates and separates the brain from the world. Since it seems to be generated within the brain itself and is apparently uncoupled from the world or environment. Recent empirical studies suggest that this is not true, though, as it is supported by a recent study of ours.
Niall Duncan from my group (Duncan et al, 2015) investigated healthy college students, (i.e. those without any neurologic, psychiatric or medial disease) with a psychological questionnaire that assessed early childhood trauma, the Childhood Trauma Questionnaire (CTQ). This questionnaire was complemented with extensive imaging. He measured the spatiotemporal structure of their brains' resting state activity using fMRI, and measured the variable of entropy. Roughly, entropy reflects the statistically-based degree of complexity (or disorder) of the signal (as measured in fMRI) across time (and space) within the brain and, more specifically, how much the signal at one point in time (and space) is different from the signal obtained at the subsequent and later points in time. Therefore, one can say that entropy can be regarded as a statistically-based measure of the temporal structure of the brain’s resting state activity.
How did the early childhood trauma affect the entropy — the temporal structure, of the brain’s intrinsic activity in a particular region — namely the perigenual anterior cingulate (the PACC is highly relevant for processing personal relevance or self-relatedness; see Northoff et al., 2006; Northoff 2014b) in later adulthood? The subjects who scored high for early childhood trauma also showed higher degrees of entropy in their PACC intrinsic activity in early adulthood. Specifically, we observed significant correlation between PACC entropy and their questionnaire score: the higher the degree of early childhood trauma, the higher the degree of PACC entropy in the brain’s intrinsic activity later in early adulthood. This result suggests that higher degrees of early childhood trauma became encoded into the temporal structure, i.e. entropy of the brain’s intrinsic activity at the time and persisted until early adulthood.
More generally, events in the world impact and modulate the brain’s intrinsic activity in such a way (i.e. in a statistically-based and spatiotemporal way) that they can become traumatic events for the respective person. The spatiotemporal structure of the brain’s intrinsic activity may therefore serve as “spatiotemporalized memory” of how the world impacted and modulated the brain and hence, more generally, of the world-brain interface. Such “spatiotemporalized memory” must obviously be distinguished from what psychologists and cognitive neuroscientists describe usually as memory: they associate memory with specific cognitive features so that one may want to speak of cognitive memory (such cognitive memory is distinct from the spatiotemporalized memory, referenced here, that remains non-cognitive or pre-cognitive). Philosophically, such a non-cognitive (or pre-cognitive) form of memory may come somewhat close to what the early 20th Century French philosopher Henri Bergson described as “memory” though that discussion remains beyond the scope of this blog.
How did Niall Duncan further support his assumption that events in early childhood, impact and modulate the brain’s intrinsic activity? In addition to temporal measures of neural activity, i.e. entropy, using magnetoresonancespectroscopy (MRS), Duncan also included biochemical measures, such as the resting state concentration of glutamate in the PACC. Glutamate is a biochemical (neurotransmitter) that is well known to be centrally involved in developing neural pathways from early childhood up until right after birth. Due to the neurodevelopmental role of glutamate, one may assume that early childhood trauma may also affect the levels of glutamate later in early adulthood.
Indeed, Duncan observed a direct relationship between early childhood trauma and glutamate: the higher the degree of childhood trauma (as measured with CTQ), the lower the resting state concentration of glutamate in PACC. This suggests that a particular event in the world can impact and modulate the biochemical features of the brain’s intrinsic activity, its level of glutamate, in such a way that the respective event may later be regarded as traumatic. Though, the exact empirical relationship between early childhood trauma and glutamate remains to be investigated. It is nevertheless clear that events with a rather complex statistical frequency distribution can also modulate and impact biochemical measures in the brain.
We have, however, omitted the question of how the changes in the brain’s intrinsic activity as related to early childhood trauma impact and modulate its subsequent functioning in later adulthood. To begin answering this question, Duncan et al. (2015) included yet another component in their imaging experiment in fMRI, namely a task that applied aversive stimuli (a short painful tactile stimulus to the index finger) and measured its stimulus-induced or task-evoked activity. Neural activity was measured specifically during the anticipation of aversive stimuli. Most interestingly, we observed that neural activity in the right anterior insula and the motor cortex during the aversive anticipation correlated significantly with all three measures: early childhood trauma, glutamate concentration, and degree of entropy. Specifically, it correlated with the relationship between early childhood trauma: the higher the degree of early childhood trauma, the lower the degree of stimulus-induced activity in the motor cortex during the anticipation of (a certain) aversive stimulus.
What do these results tell us about the brain in general? The brain and especially its spontaneous activity are highly sensitive to experiences in the environment. They are experience-dependent and these experiences are apparently encoded spatiotemporally, amounting to spatiotemporal memory. Childhood trauma is encoded in our brain’s spontaneous activity in adulthood. Therefore we can never forget it and it impacts all our actions and experiences in the present, like the reaction to aversive stimuli. For that reason we sometimes need therapy to deal with our early childhood experiences in order to modulate and change the spatiotemporal memory of our brain’s spontaneous activity.
Duncan NW, Hayes DJ, Wiebking C, Tiret B, Pietruska K, Chen DQ, Rainville P, Marjańska M, Ayad O, Doyon J, Hodaie M, Northoff G. (2015)
Negative childhood experiences alter a prefrontal-insular-motor cortical network in healthy adults: A preliminary multimodal rsfMRI-fMRI-MRS-dMRI study.
Hum Brain Mapp. 2015 Aug 19. doi: 10.1002/hbm.22941. [Epub ahead of print]
The PDF of the paper can be obtained at my website: www.georgnorthoff.com
These and other results start revealing the brain and especially its spontaneous activity, and how it is shaped by our experience in the world. In the coming months, I will lead you even deeper into the brain’s spontaneous activity and show how it is related to our sense of self.