The Physiology of Human Language & Speech: The Brain & Nervous System

Instructor: Sunday Moulton

Sunday recently earned a PhD in Anthropology and has taught college courses in Anthropology, English, and high school ACT/SAT Prep.

In this lesson, learn about the role of the brain and nervous system in language and speech. We'll explore different regions of the brain, how they acquire, process, or produce language data, and the nerves we use to make speech.

The Left Hemisphere of the Brain

You've probably heard people refer to themselves as 'left-brained' or 'right-brained', meaning their skill strengths align with the tasks associated with one hemisphere of the brain or the other.

When the tasks involve speech, the majority of activated brain regions appear on the left side of the brain. This side is most often related to linear concepts like time, step-by-step instructions, and language.

Cortical regions of the brain involved in speech and language.
Cortical Regions

Language Input

When language is used to convey information to us, the activated part of the brain depends on the means of input.

  • Reading words or viewing sign languages uses the optic nerves and the visual cortex in the brain.
  • Spoken language uses the auditory nerves and the auditory cortex.

These two cortices interpret what we see and hear, recognizing familiar shapes and sounds. However, they cannot interpret the meaning of what we see and here. This belongs to other parts of the brain.

Language Cortex

An important part of the cerebral cortex is the language cortex. This area contains the key parts of the brain responsible for processing language-related sensory input as well as combining language components to produce language output.

The Wernicke's area is the main receptive component, but it cannot do the job alone. With the help of the angular gyrus, insular cortex, and basal ganglia, the Wernicke's area attaches the meaning to word sounds and shapes. It also incorporates context into the interpretation.

The Broca's area is the primary output component of the language cortex. This area assembles the words related to our meaning, so our spoken or written expressions convey a message instead of nonsense.

While other lessons look in-depth at the Wernicke's area and the Broca's area, let's take a look at the parts of the brain playing a supportive role in the language cortex.

  • Angular gyrus: performs several functions in connection with other brain regions in order to process language, numbers, spatial awareness, and memory.
  • Insular cortex: involved with context and perception, self-awareness, interaction with other people, movement, and understanding.
  • Basal ganglia: a clustered group of neurons which, until recently, was primarily associated with motor function. Today, however, researchers are finding evidence that the basal ganglia also help to process emotional content of language, the motives and meaning of others and to direct or filter cognitive information.

Basal Ganglia
Basal Ganglia

Motor Cortex

Even if we know exactly what to say, we could never speak without the motor cortex, a region of the frontal lobe responsible for operating nerves related to motion. We have many moving parts when we speak but three nerves in particular are vital to controlling different parts of our physiology of speech.

Phrenic Nerve
Phrenic Nerve

  1. Phrenic nerve: both a sensory and motor nerve that controls the diaphragm, moving it to power the inhalation and exhalation of air in our lungs.
  2. Laryngeal nerves: a complex assortment of tissues in our throat that creates the vibrations necessary for the human voice. The larynx itself is controlled by the superior laryngeal nerve, which branches into the internal laryngeal nerve to send data to the brain and the external laryngeal nerve that provides motor control to the larynx.
  3. Hypoglossal nerve: the nerve tasked with the motor function of the tongue, without which we would be unable to speak.

Hypoglossus Nerve
Hypoglossus Nerve

Language Learning and Mirror Neurons

Now that we know the parts of the brain involved in language input, processing, and output, as well as the nerves related to the moving parts of speech production, we're still left with one last question. How do we, neurologically, develop language skills in the first place? What goes on in our brains to make it all possible? Recent studies indicate this has a lot to do with mirror neurons.

We've known for a while that mirror neurons play a role in learning actions and developing empathy. They activate parts of our brains related to the scene we are watching, mirroring the action in our mind without physically recreating the action.

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