What happens if you surgically remove the hippocampus from brain?
Surgical removal of the hippocampus from the brain, a procedure called hippocampectomy, has significant effects on memory and cognitive function. The hippocampus is a crucial structure within the medial temporal lobe of the brain, primarily responsible for the formation and consolidation of new memories. Here are some of the consequences of surgically removing the hippocampus:
1. Anterograde Amnesia:
Hippocampectomy leads to anterograde amnesia, which is the inability to form new memories after the surgery. Individuals with removed hippocampi can recall events that happened before the surgery but have difficulty encoding and storing new information. This memory impairment is particularly evident for explicit or declarative memories, which involve conscious recollection of facts and events.
2. Impaired Spatial Navigation:
The hippocampus plays a vital role in spatial navigation and cognitive mapping. It helps individuals understand their location in relation to their surroundings and navigate through space effectively. Removing the hippocampus can result in difficulties with spatial orientation, route learning, and spatial memory tasks.
3. Disruption of Episodic Memory:
Episodic memory refers to the ability to remember specific events, including the associated time, place, and emotional context. The hippocampus is critical for integrating these elements and creating cohesive episodic memories. Without a functional hippocampus, individuals may struggle to recall personal experiences in detail.
4. Preserved Procedural Memory:
In contrast to anterograde amnesia for declarative memories, procedural memory remains largely intact after hippocampectomy. Procedural memory involves learning and retaining motor skills, habits, and routines that become automatic over time. This is because procedural memories are processed and stored in different brain regions, such as the basal ganglia and the cerebellum.
5. Emotional Disturbances:
The hippocampus has connections to the amygdala, a brain structure associated with emotional processing and fear conditioning. Removing the hippocampus can affect emotional regulation, resulting in reduced emotional responsiveness, blunted affect, and a diminished ability to experience and express emotions.
6. Difficulty with Contextual Learning:
The hippocampus is involved in contextual learning, which is the association between specific information and the context in which it was learned. Hippocampectomy can lead to impairments in contextual memory, making it harder for individuals to recall information based on its context.
7. Impact on Long-Term Memory Consolidation:
The hippocampus acts as a temporary storage site for newly acquired memories, allowing their consolidation and transfer to long-term memory. Without the hippocampus, new memories may not be effectively consolidated, resulting in long-term memory deficits.
It's important to note that the effects of hippocampectomy can vary among individuals, and compensatory mechanisms in other brain regions may mitigate some of these deficits. However, surgically removing the hippocampus has profound consequences on memory and cognitive abilities, especially in the domains of new memory formation and spatial navigation.