Trends in Cognitive Sciences
ReviewExperience-dependent structural plasticity in the adult human brain
Section snippets
Structural and functional plasticity in the brain
An intrinsic property of the human central nervous system is the lifelong ability for structural and functional brain reorganization [1]. The term ‘plasticity’ refers to functional or structural changes (which may trigger each other) that occur in the adult brain to adjust to changes in the external environment or internal milieu 2, 3. The extent of plastic reorganization is conditional on the relevance of the alterations for the individual and can have either beneficial or maladaptive
The neuroanatomical basis of structural brain plasticity
During the past decade, a steadily growing number of studies in primate and nonprimate animals confirm the notion that experience, learning new skills but also damage of the nervous system, can cause functional and structural reorganization of the brain. At the functional level it has been convincingly demonstrated that even loss of sensory input due to peripheral nerve lesion can induce reorganization of cortical representation fields 17, 18, 19, 20. At the structural level, these studies
Cross-sectional differences: the hen or the egg?
A vast number of cross-sectional morphometric studies (Box 1) have demonstrated neuroanatomical correlates of learning and experience in different cognitive domains. For example, navigational experience has been reported to be correlated with posterior hippocampus size [14] and musical proficiency to be associated with volume enlargement of motor and auditory areas and their anatomical connections 10, 26, 46. More recent studies discussed morphological enlargement in the cerebellar vermian
Dynamic changes in human brain structure
Longitudinal studies in which imaging data are acquired at multiple time points during experimental intervention have the potential to unveil dynamic properties of learning-related plastic changes. The first longitudinal studies investigated a specific learning paradigm, namely 3-ball cascade juggling [7]. Juggling represents a complex visuomotor task, where perception and anticipation of moving targets determine the planning of subsequent motor action. Daily training for three months assured
Learning and experience shaping the brain
Several studies have built on and extended the findings in procedural learning 45, 58, 59, 60, 61 by studying longitudinally morphometric changes related to memory and learning. The first study of this type investigated a ‘real-life’ situation: the German basic medical exam, called ‘Physikum’ [8], which includes both oral and written tests in biology, chemistry, biochemistry, physics, social sciences, psychology, human anatomy and physiology demanding a high level of encoding, retrieval and
Physical exercise: shaping the brain or the mind or both?
Physical activity and an enriched environment have been shown to improve the rate of adult neurogenesis and maintenance of these new neurons 37, 66. A recent study demonstrating in vivo correlates of physical exercise-induced changes in the hippocampus confirms the theoretical possibility of angiogenesis/neurogenesis underlying plasticity processes [67]. Interestingly, these findings have been replicated in older and aged animals [68], suggesting that age is not per se a limiting factor for
Maladaptive plasticity: the flip side of the coin
Maladaptive plasticity can be defined as behavioral loss or even the development of disease symptoms resulting from plasticity changes in the adult human brain. Recent studies provide sufficient evidence that faulty practice or excessive demand could pose a risk of maladaptive plasticity depending on individual predisposition [73]. Animal models demonstrate that repetitive somatosensory stimulation of the fingers in primates results in abnormal hand postures similar to the clinical picture of
Cellular events underlying experience-dependent structural plasticity
The first study describing subtle anatomical changes using morphometry (in this case VBM) in patients was published in 1999 [84] and despite several hundred studies published since then, the nature of the underlying cellular events is still essentially unknown. In some respects, this situation resembles that in the functional MRI-field some years ago, when its use for our understanding of brain function was unquestioned, yet the long-supposed physiological correlate of the blood oxygen
Concluding remarks
Technical advances in live imaging studies and molecular approaches have contributed significantly to our current understanding of developmental plasticity and also focused our attention on plasticity exhibited by the mature brain. Neuroplasticity can be understood as the environmentally driven constant rearrangement of network homeostasis balancing the integration of neuronal activity, neurotransmitter release, neuronal (and perhaps glial) morphogenesis and changes in network formation
Acknowledgments
The author wishes to thank Gerd Kempermann, Christian Gaser and Bogdan Draganski for valuable discussion and input.
Glossary
- Adult neurogenesis
- a specific case of cell-based brain plasticity where new neurons (and not only neurites and synapses) are added to the brain network in an activity-dependent way. In humans, new neurons are generated throughout life in the hippocampal region, which is thought to provide the functional backbone for learning and memory. Recent animal and human studies have proposed the hippocampus and neurogenesis a prime target in a number of diseases, most notably dementias as well as major
References (97)
Neuronal plasticity as an adaptive property of the central nervous system
Ann. Anat.
(1992)Interhemispheric transfer time and structural properties of the corpus callosum
Neurosci. Lett.
(2006)- et al.
Training-induced structural changes in the adult human brain
Behav. Brain Res.
(2008) - et al.
Reorganization of neocortical representations after brain injury: a neurophysiological model of the bases of recovery from stroke
Prog. Brain Res.
(1987) Anatomical correlates of learning novel speech sounds
Neuron
(2002)Voxel-based morphometry reveals increased gray matter density in Broca's area in male symphony orchestra musicians
Neuroimage
(2002)Towards a neuroimaging biomarker for amyotrophic lateral sclerosis
Lancet Neurol.
(2011)Subcortical contributions to massive cortical reorganizations
Neuron
(1999)CRE-mediated gene transcription in neocortical neuronal plasticity during the developmental critical period
Neuron
(1999)Long-term environmental enrichment leads to regional increases in neurotrophin levels in rat brain
Exp. Neurol.
(2000)