The hippocampus is a complex brain structure embedded deep within the temporal lobe. This seahorse-shaped structure has two curved components, one in each hemisphere. Hippocampal volume refers to the overall size of this brain region. Its size indicates brain health and function.
The Hippocampus and Its Core Functions
The hippocampus plays significant roles in cognitive processes. One primary function involves consolidating information, transforming short-term into long-term memories. It organizes new factual information and events (declarative memories).
This brain structure also serves as the brain’s internal navigation system. Specialized neurons, called place cells, fire in specific locations, contributing to a cognitive map. It interacts with other brain regions for spatial memory and navigation.
Beyond memory and navigation, the hippocampus participates in general learning processes. It supports the acquisition of new information and skills, forming new neural connections.
Factors That Change Hippocampal Size
The hippocampus exhibits plasticity. Chronic stress, for instance, can negatively impact hippocampal volume, partly due to prolonged exposure to hormones like cortisol. Sustained stress can lead to changes in neuronal morphology and suppress neurogenesis, potentially reducing hippocampal size.
A sedentary lifestyle and insufficient sleep decrease hippocampal volume. Physical inactivity and chronic sleep restriction can reduce hippocampal volume. The natural aging process leads to a gradual reduction in hippocampal volume, with older adults experiencing a 1-2% loss each year.
Conversely, lifestyle factors can preserve or increase hippocampal size. Regular aerobic exercise can increase hippocampal volume, particularly in older adults, and may reverse age-related volume loss. This benefit is linked to increased levels of brain-derived neurotrophic factor (BDNF), a protein that supports neuron development and neurogenesis.
Engaging in continuous learning and acquiring new complex skills supports hippocampal health. Activities like memorizing poetry or learning a musical instrument stimulate brain activity, promoting hippocampal integrity. Mindfulness and meditation practices may contribute to hippocampal volume by reducing stress and fostering beneficial brain changes.
Connection to Neurological and Mental Health
Hippocampal volume changes are observed in neurological and mental health conditions. In Alzheimer’s disease, significant hippocampal atrophy is an early and prominent marker. This reduction is due to neurodegeneration and correlates with memory loss and disorientation in early stages.
Smaller hippocampal volume is linked to major depressive disorder (MDD). Patients with depression often exhibit a 10-15% reduction in hippocampal volume. This structural alteration is ongoing research, contributing to understanding the neurobiological underpinnings of mood disorders.
Post-traumatic stress disorder (PTSD) is also associated with reduced hippocampal volume. A correlation exists between smaller hippocampal size and PTSD, though whether it’s a predisposing factor or a consequence of trauma is still investigated. These volume changes underscore the hippocampus’s sensitivity to neurodegenerative processes and psychological distress.
How Hippocampal Volume Is Measured
Hippocampal volume is measured using non-invasive neuroimaging techniques, primarily Magnetic Resonance Imaging (MRI). High-resolution MRI scans capture detailed images of the brain, allowing precise visualization of its structures. These images are then processed using specialized software for volumetric analysis.
Scientists and clinicians use software like FreeSurfer or Neuroreader to automatically segment and calculate hippocampal volume from MRI data. These tools use algorithms comparing the brain image to anatomical atlases or previously segmented images to delineate hippocampal boundaries. The calculated volume is compared to normative data for age and other factors. No single “perfect” hippocampal volume exists; interpretation relies on context, including age, population averages, and changes over time.