Speech & Language
Speech and language difficulty commonly affects individuals with dementia and other neurological conditions.

Speech and language difficulty commonly affects individuals with dementia and other neurological conditions. Patients may experience deficits in the form of verbal expression (i.e., word-finding difficulty) or comprehension (i.e., difficulty understanding speech).


Language is made up of socially shared rules that include the following:

  • Semantics or meaning (e.g., “stern” can mean “severity of manner” or “the back of a boat”)
  • How to make new words (e.g., friend, friendly, unfriendly)
  • Grammar (e.g., “I walked to the new restaurant” rather than “walk I restaurant new”)
  • Social context (e.g., “Could you please open the window?” versus “Hey, open the window now!”)


Speech is the verbal means of communicating. Speech consists of the following:

  • Articulation: How speech sounds are made
  • Voice: The use of the vocal folds and breathing to produce sound (e.g., hoarseness, breathiness, projection)
  • Fluency and prosody: The rhythm, intonation, stress, and related attributes of speech

When someone has trouble understanding other people (receptive language) or explaining thoughts, ideas and feelings (expressive language), that is a language disorder.

When someone cannot produce speech sounds correctly or fluently or has voice problems, that is a speech disorder.

Anatomy of Language

There are several areas of the brain that play a critical role in speech and language.

  • Broca’s area, located in the left hemisphere, is associated with speech production and articulation. Our ability to articulate ideas, as well as use words accurately in spoken and written language, has been attributed to this crucial area.
  • Wernicke’s area is a critical language area in the posterior superior temporal lobe connects to Broca’s area via a neural pathway. Wernicke’s area is primarily involved in the comprehension. Historically, this area has been associated with language processing, whether it is written or spoken.
  • The angular gyrus allows us to associate multiple types of language-related information whether auditory, visual or sensory. It is located in close proximity to other critical brain regions such as the parietal lobe which processes tactile sensation, the occipital lobe which is involved in visual analyses and the temporal lobe which processes sounds. The angular gyrus allows us to associate a perceived word with different images, sensations and ideas.

Disorders of Speech & Language

Aphasia is the term used to describe an acquired loss of language that causes problems with any or all of the following: speaking, listening, reading and writing. Some people with aphasia have trouble using words and sentences (expressive aphasia). Some have problems understanding others (receptive aphasia). Others with aphasia struggle with both using words and understanding (global aphasia). Aphasia can cause problems with spoken language (talking and understanding) and written language (reading and writing). Typically, reading and writing are more impaired than talking or understanding. The severity of the aphasia depends on the amount and location of the damage to the brain.

Broca’s (expressive or motor) Aphasia

Damage to a discrete part of the brain in the left frontal lobe (Broca’s area) of the language-dominant hemisphere has been shown to significantly affect the use of spontaneous speech and motor speech control. Words may be uttered very slowly and poorly articulated. Speech may be labored and consist primarily of nouns, verbs or important adjectives. Speech takes on a telegraphic character. People suffering from Broca’s aphasia have great difficulty with repetition and a severe impairment in writing. In some patients, however, the understanding of spoken and written language may be relatively well-preserved. The nonfluent variant of primary progressive aphasia (nfvPPA) is a type of expressive aphasia.

Global Aphasia

If damage encompasses both Wernicke’s and Broca’s areas, global aphasia can occur. In this case, all aspects of speech and language are affected. Patients can say a few words at most and understand only a few words and phrases. They usually cannot carry out commands or name objects. They cannot read or write or repeat words said to them.

Logopenic Primary Progressive Aphasia (lvPPA)

Degeneration of the angular gyrus in the temporal lobe and inferior parietal lobe can lead to lvPPA. Typical symptoms include slowed speech with normal articulation, impaired comprehension of sentence syntax as well as impaired naming of things. lvPPA is probably associated with Alzheimer’s disease pathology.

Primary Progressive Aphasia (PPA)

PPA is caused by degeneration in the parts of the brain that control speech and language (the left, or “dominant,” side of the brain in the frontal, temporal and parietal regions that normally control language function). This type of aphasia begins gradually, with speech or language symptoms that reflect the normal role for the site of initial degeneration. Eventually, problems spread throughout the broader language network. PPA subtypes include nonfluent primary progressive aphasia (nfvPPA), semantic variant primary progressive aphasia (svPPA) and logopenic primary progressive aphasia (lvPPA). These syndromes result from a variety of underlying diseases, but most often frontotemporal lobar degeneration (FTLD) (both tau and TDP-43 subtypes) or Alzheimer’s disease.

Wernicke’s Aphasia

Damage to the posterior superior areas of the language dominant temporal lobe (often called Wernicke’s area) has been shown to significantly affect speech comprehension. In other words, information is heard through an intact auditory cortex in the anterior temporal lobe, however, when it arrives at the posterior association areas, the information cannot be sufficiently “translated.” In contrast to Broca’s aphasia, the person with Wernicke’s aphasia talks volubly and gestures freely. Speech is produced without effort, and sentences are of normal length. However, the person’s speech is devoid of meaning.

This pattern of receptive aphasia is marked by:

  • Fluent, grammatically correct speech with little meaning
  • Poor comprehension
  • Paraphasic errors:
    • calling a spoon a “fork” (semantic)
    • calling a spoon a “spood” (literal)
  • Neologisms (or nonsense words)

Impact of Neurological Illness

Alzheimer’s Disease (AD)

In Alzheimer’s disease, the most common cause of dementia, language functioning may be relatively spared in the early stages of the disease, but it is likely to decline substantially in the mid to late stages. People with AD often have difficulty with language expression, word fluency and naming objects. Syntax and comprehension of language are generally preserved in the early stages, however, in the later stages, speech may become halting due to word-finding difficulties. In other words, patients have great difficulty speaking in full sentences because of the effort that is required to find the right words. Writing skills may often be compromised. Speech comprehension may be significantly impaired during the end-stage of the disease.

Corticobasal Syndrome (CBS)

CBS most commonly involves difficulty with language expression, such as word finding difficulty or speech articulation problems. Reading and writing may also be impaired.

Frontotemporal Dementia (FTD)

Language is generally not primarily affected in the behavioral variant of FTD. Often, people with bvFTD are quiet and talk less, but this change derives more from increased apathy and lack of initiation. Patients may respond when spoken to but tend to otherwise be disinclined to speak. On the other hand, some patients experience euphoria and disinhibition as the disease progresses, and these people may be inclined to talk more.

The initial symptoms of semantic variant PPA often involve problems with finding the right words during conversation. Bilateral deterioration of the temporal lobes (particularly anterior) leads to:

  • fluent speech production,
  • grammatically correct language,
  • loss of word and object meaning,
  • relatively preserved comprehension and
  • deficits in comprehending the emotions of others.

People with nonfluent variant PPA develop difficulties producing speech. They know what they want to say, but they have immense trouble getting the words out of their mouths. The degeneration of cortex in the language-dominant areas of the frontal, parietal and temporal lobes (including Broca’s area) leads to:

  • slow, labored non-fluent speech,
  • agrammatism (use of high-value content words only without connecting or descriptive words) and
  • relatively preserved word comprehension.

Stroke & Injury

Individuals who have suffered neurological injuries, such as stroke or traumatic brain injury, may also experience speech and language deficits, particularly but not exclusively, if the left side of the brain was affected. Aphasia is common in people who have left sided brain injuries. Speaking, listening, reading, and writing skills may all be affected to varying degrees. Should the stroke affect the parts of the brain that control muscles used in speech (those in tongue, mouth and lips), speech can become slurred or slowed.