PSY 3740 Module 5 Cognitive Functioning Paper: Long-Term Potentiation, the Molecular Basis of Memory and Broca's Patients Revisited Example

Strengthened Synapses and Lost Words: The Biology of Memory and Language

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Bachelor of Arts in Psychology, Thomas Edison State University

PSY-3740: Physiological Psychology

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Month Day, Year

Strengthened Synapses and Lost Words: The Biology of Memory and Language

Introduction

My neighbor, a retired teacher, had a stroke in the left side of his brain last spring. He understands what I say and knows what he wants to say, but words come out slowly, in short phrases, with great effort. His speech therapist called it Broca's aphasia. At the same time, I have been studying for exams and wondering what happens in my brain when I remember something. This paper examines the biological basis of two cognitive functions, memory and language.

Learning Changes Synapses

In 1949, Donald Hebb proposed that when one neuron repeatedly helps fire another, the connection between them strengthens. This idea, often summarized as "cells that fire together wire together," suggested that learning might be stored in changing synapses. For decades, it remained a theory.

Long-Term Potentiation

Bliss and Lømo (1973) provided the first strong evidence. In anesthetized rabbits, they stimulated a pathway leading into the hippocampus, called the perforant path, and recorded responses in the dentate gyrus. After brief bursts of high-frequency stimulation, the responses to ordinary single stimuli became larger and stayed larger for hours, in some animals much longer. They called this long-lasting potentiation, now known as long-term potentiation, and suggested that it could be a mechanism for learning in the hippocampus, a structure already linked to memory by studies of patients such as H.M.

Memory at the Molecular Level

Kandel (2001) summarized decades of research on the sea slug Aplysia, whose simple nervous system and large neurons allowed his team to trace learning to individual synapses. When the animal learns to withdraw its gill more strongly after a shock, a form of learning called sensitization, the connection between sensory and motor neurons strengthens. Short-term memory, lasting minutes, involves chemical modification of proteins already present at the synapse, increasing neurotransmitter release. Long-term memory, lasting days or longer, requires a further step: signals travel to the nucleus, where they switch on genes through a protein called CREB, leading to the growth of new synaptic connections. Kandel argued that this distinction, between modifying existing proteins and building new structures, holds in mammals as well, and it earned him a Nobel Prize.

Practical Lessons for Learning

The biology fits with research on effective study. Repeated, spaced practice, rather than cramming, gives synapses repeated opportunities to strengthen and allows the slower processes of gene expression and synapse growth that long-term memory requires. Sleep, as the previous module showed, also supports consolidation.

Language and Broca's Area

In 1861, Paul Broca examined a patient named Leborgne who could produce only a single syllable, "tan," but seemed to understand language. After Leborgne died, Broca found damage in the left frontal lobe and argued that this region was essential for speech production. A second patient, Lelong, had similar problems and damage in a similar area. This region became known as Broca's area, and the left hemisphere's role in language became one of the foundations of neuropsychology.

Broca's Patients Revisited

Dronkers et al. (2007) obtained permission to scan the preserved brains of Leborgne and Lelong, kept in a Paris museum, using high-resolution MRI. They found that the lesions extended deeper and more widely than Broca had described, involving regions beneath the surface and white matter pathways that connect language areas. In Lelong's brain, the damage did not include the full region now called Broca's area. The authors concluded that speech production depends on a broader network than a single area and that the classic model linking one area to one function was too simple.

Understanding My Neighbor

My neighbor's difficulty producing speech, while understanding remains largely intact, fits the pattern Broca described. Dronkers and colleagues' findings suggest that his stroke likely affected a network rather than a single spot, which may explain why aphasia varies so much between patients. Wernicke's aphasia, associated with damage to the left temporal lobe, shows the opposite pattern: fluent but often meaningless speech and poor comprehension.

Plasticity and Recovery

The same synaptic plasticity that underlies learning supports recovery after stroke. With intensive speech therapy, surviving parts of the language network and areas in the right hemisphere can take on new roles. My neighbor's therapist has him practice phrases repeatedly, an approach consistent with the biology of strengthening synapses through repetition.

Working Memory and the Prefrontal Cortex

Memory also includes working memory, the ability to hold and manipulate information for a short time, such as keeping a phone number in mind while dialing. Working memory depends heavily on the prefrontal cortex and its connections, and it is limited in capacity, which is why studying while distracted is less effective.

Wernicke's Area and the Language Network

In 1874, Carl Wernicke described patients with damage to the left temporal lobe whose speech was fluent but often meaningless and who had trouble understanding others. Later models linked Broca's and Wernicke's areas with a bundle of fibers called the arcuate fasciculus. Dronkers and colleagues' findings fit a modern view in which language relies on a network of regions and connections in both frontal and temporal lobes.

Limits

Long-term potentiation in rabbits and memory in sea slugs are models, and the link between LTP and actual memories in humans is supported but indirect. Dronkers and colleagues examined only two brains.

Conclusion

Bliss and Lømo showed that synapses can be strengthened for hours by patterned activity, Kandel showed that long-term memory requires new genes and new synaptic connections and Dronkers and colleagues showed that Broca's famous patients had damage across a broader language network. Memory and language both depend on changeable synapses and connected networks, which is why practice helps both a student studying for exams and a stroke survivor relearning speech.

References

Bliss, T. V. P., & Lømo, T. (1973). Long-lasting potentiation of synaptic transmission in the dentate area of the anaesthetized rabbit following stimulation of the perforant path. Journal of Physiology, 232(2), 331-356. https://doi.org/10.1113/jphysiol.1973.sp010273

Dronkers, N. F., Plaisant, O., Iba-Zizen, M. T., & Cabanis, E. A. (2007). Paul Broca's historic cases: High resolution MR imaging of the brains of Leborgne and Lelong. Brain, 130(5), 1432-1441. https://doi.org/10.1093/brain/awm042

Kandel, E. R. (2001). The molecular biology of memory storage: A dialogue between genes and synapses. Science, 294(5544), 1030-1038. https://doi.org/10.1126/science.1067020