KC (patient)
Encyclopedia
Patient KC is a widely studied Canadian memory disorder
patient who has been used as a case study in over 20 neuropsychology papers over the span of the past 25 years. In 1981, KC was involved in a motorcycle accident that left him with severe anterograde amnesia
, as well as temporally graded retrograde amnesia
. Unlike other amnesic patients (patient HM, for example), KC has his semantic memory
intact, but lacks episodic memory
with respect to his entire past. As a case study, patient KC has been linked to the breakdown of the single-memory single-locus hypothesis regarding amnesia, which states that an individual memory is localized to a single location in the brain.
Currently at age 59 , KC lives with his parents in their original home in the Toronto suburbs during the winter and spring, and at his family’s summer cottage during the summer and fall. He is single and has no children. In his spare time, he volunteers at his local library and goes on outings with other head-injury patients. He also continues to play the organ and play card games on the computer. Other than his amnesia (now stabilized), KC is in good health and is able to live a relatively normal life.
. Upon arrival at a hospital, KC was experiencing clonic
epileptic seizures and was unconscious. Surgery to remove a left-side subdural hematoma
was successful. After a few days in the hospital KC was able to respond to simple commands. After one week he was able to recognize his mother. A follow up CT scan revealed a chronic bilateral frontal subdural hematoma, enlarged ventricle
s and sulci
, and left occipital lobe
infarction
.
Upon arrival at a rehabilitation facility, KC was able to recognize friends and family, but still exhibited slower thinking ability, as well as partial right side paralysis
and vision problems with his right eye. Upon his discharge from the rehabilitation facility in July 1982, the full extent of KC’s neurological injuries was determined. He has severe injury to his medial temporal lobes, along with almost complete bilateral hippocampal loss. Ultimately, his neurological profile has stabilized, as seen in CT scans he has received once a decade since the accident.
and noetic consciousness remained unimpaired. To illustrate this, research conducted on K.C. has shown that he is able to recall factual information that he learned prior to his accident, such as his ability to know the difference between stalactites and stalagmites. However, he is unable to remember emotional details of events from his past such as his brother’s death, the September 11 attacks, and a dangerous fall he had at his home.
K.C. also suffers from severe impairment of his Autonoetic consciousness
. This means that he is unable to envision himself in the future. When asked what he would be doing later in a given day, month, or even a year, he was unable to respond with an answer. Just as he cannot remember being physically involved with events from his past, he is unable to imagine future events. Ultimately, he loses any memory of his current actions once his thoughts are directed elsewhere.
Neuropathologically, K.C suffers from both anterograde amnesia and temporally graded retrograde amnesia. Both forms of amnesia are characterized by damage to the medial temporal lobes, specifically within the hippocampal region. The trauma caused by K.C.’s accident has left him with severe anterograde amnesia that has made it impossible for him to remember both new personal experiences and semantic information. As far as his temporally graded retrograde amnesia is concerned, he is considered an anomaly; in other words, his ability to recall events prior to the accident is dependent on when those events occurred. Although he cannot remember personally experienced events, his semantic knowledge prior to his accident remained intact. His recollection of factual information in areas such as math, history and science, for example, were unaffected.
, research suggests that this area functions in processing episodic memory. However, damage to this area has left his semantic memory fully intact. This implies that episodic and semantic components of memory could be formed and stored separately, and thus processed by different regions of the brain.
studies on Patient K.C. revealed that individuals with severe amnesia can display intact priming capabilities regardless of episodic memory damage. Priming involves initially exposing a subject to a word or image so that a memory of that word or image can be formed. This is meant to improve a subject's recall of that word or image when that word or image is shown at a later time. Patient K.C. additionally showed that priming effects can last for long periods of time; in one study, researchers presented K.C. with a list of words, and after 12 months showed him the same words with letters missing. K.C. was able to complete these fragmented words as successfully as a person with normal brain function who was shown the same list initially. This challenged the previous opinion that patients with anterograde amnesia are incapable of adding information to their declarative memory
.
Even though K.C. could not remember the actual teaching sessions, he was able to retain the raw information—the three-word sentences—presented to him. This showed that episodic and semantic memory are independent of one another, because K.C.’s episodic memory was not intact, but his declarative memory still functioned correctly. These findings show that acquisition of semantic knowledge is possible even if episodic memory is absent.
Research on Patient K.C. also led to greater understanding of priming in amnesics. Priming involves the exposure of a person to information under false pretenses. This information is ultimately recalled at a later period with the hope that the previous priming will improve recall ability. With respect to patient K.C., researchers found that successful priming is independent of both semantic and episodic memory. Episodic and semantic memory are therefore described as showing stochastic independence, ruling out the idea that K.C. was able to retain information because certain words were of greater significance to him than others.
Studies on K.C.’s semantic learning also provided insight into the conditions that are necessary to promote successful semantic learning in amnesic patients. Researchers found that maximizing amnesics’ ability to obtain new information requires efforts to minimize interference, which occurs when previously learned information prevents patients from correctly remembering subsequent information. The finding that interference significantly prevents successful semantic learning in amnesics provided explanation for why earlier experiments failed, as they did not make efforts to minimize interference.
Patient K.C.'s learning of this more complex information, however, was hyperspecific. When asked general questions about his tasks, K.C. could not explain the meaning behind the new information he had gained about computers. Similarly, if the command instructions he had learned were slightly changed, K.C. was unable to perform the programming tasks. This reflects that K.C. did not learn the meaning behind the information he had learned, and that he had formed only simple stimulus response connections. K.C.’s amnesia therefore involved both information loss and impairment of the processes that allow the integration of information to create an interconnected memory. Nevertheless, K.C. showed that severe anterograde amnesia does not restrict individuals from retaining knowledge that is more complex than information learned from priming.
Memory disorder
Memory can be defined as an organism's ability to encode, retain, and recall information. Disorders of memory can range from mild to severe, yet are all a result of damage to neuroanatomical structures; either in part or in full. This damage hinders the storage, retention and recollection of memories...
patient who has been used as a case study in over 20 neuropsychology papers over the span of the past 25 years. In 1981, KC was involved in a motorcycle accident that left him with severe anterograde amnesia
Anterograde amnesia
Anterograde amnesia is a loss of the ability to create new memories after the event that caused the amnesia, leading to a partial or complete inability to recall the recent past, while long-term memories from before the event remain intact. This is in contrast to retrograde amnesia, where memories...
, as well as temporally graded retrograde amnesia
Retrograde amnesia
Retrograde amnesia is a loss of access to events that occurred, or information that was learned, before an injury or the onset of a disease....
. Unlike other amnesic patients (patient HM, for example), KC has his semantic memory
Semantic memory
Semantic memory refers to the memory of meanings, understandings, and other concept-based knowledge unrelated to specific experiences. The conscious recollection of factual information and general knowledge about the world is generally thought to be independent of context and personal relevance...
intact, but lacks episodic memory
Episodic memory
Episodic memory is the memory of autobiographical events that can be explicitly stated. Semantic and episodic memory together make up the category of declarative memory, which is one of the two major divisions in memory...
with respect to his entire past. As a case study, patient KC has been linked to the breakdown of the single-memory single-locus hypothesis regarding amnesia, which states that an individual memory is localized to a single location in the brain.
Biography
KC was born in 1951 as the oldest of five children and grew up in the suburbs of Toronto, Canada. After attending a community college to study business administration he obtained a job at a manufacturing plant, which he held until the time of his motorcycle accident.Currently at age 59 , KC lives with his parents in their original home in the Toronto suburbs during the winter and spring, and at his family’s summer cottage during the summer and fall. He is single and has no children. In his spare time, he volunteers at his local library and goes on outings with other head-injury patients. He also continues to play the organ and play card games on the computer. Other than his amnesia (now stabilized), KC is in good health and is able to live a relatively normal life.
Accident and neurological damage
In October 1981, KC was involved in a single-vehicle accident on his way home from his job at the manufacturing plant when the motorcycle he was riding veered off of an exit ramp. He suffered a traumatic brain injuryTraumatic brain injury
Traumatic brain injury , also known as intracranial injury, occurs when an external force traumatically injures the brain. TBI can be classified based on severity, mechanism , or other features...
. Upon arrival at a hospital, KC was experiencing clonic
Clonus
Clonus is a series of involuntary muscular contractions and relaxations. Clonus is a sign of certain neurological conditions, and is particularly associated with upper motor neuron lesions such as in stroke, multiple sclerosis, spinal cord damage and hepatic encephalopathy...
epileptic seizures and was unconscious. Surgery to remove a left-side subdural hematoma
Subdural hematoma
A subdural hematoma or subdural haematoma , also known as a subdural haemorrhage , is a type of haematoma, a form of traumatic brain injury. Blood gathers within the outermost meningeal layer, between the dura mater, which adheres to the skull, and the arachnoid mater, which envelops the brain...
was successful. After a few days in the hospital KC was able to respond to simple commands. After one week he was able to recognize his mother. A follow up CT scan revealed a chronic bilateral frontal subdural hematoma, enlarged ventricle
Ventricle
Ventricle may refer to:* Ventricle , the pumping chambers of the heart* Ventricular system in the brain* Ventricle of the larynx, a structure in the larynx* Stomach of the gastrointestinal tract...
s and sulci
Sulcus (anatomy)
A sulcus is a depression or fissure in the surface of an organ, especially the brain.-Elsewhere:* anterior interventricular sulcus* calcaneal sulcus* coronal sulcus* gingival sulcus* gluteal sulcus* interlabial sulci...
, and left occipital lobe
Occipital lobe
The occipital lobe is the visual processing center of the mammalian brain containing most of the anatomical region of the visual cortex. The primary visual cortex is Brodmann area 17, commonly called V1...
infarction
Infarction
In medicine, infarction refers to tissue death that is caused by a local lack of oxygen due to obstruction of the tissue's blood supply. The resulting lesion is referred to as an infarct.-Causes:...
.
Upon arrival at a rehabilitation facility, KC was able to recognize friends and family, but still exhibited slower thinking ability, as well as partial right side paralysis
Paralysis
Paralysis is loss of muscle function for one or more muscles. Paralysis can be accompanied by a loss of feeling in the affected area if there is sensory damage as well as motor. A study conducted by the Christopher & Dana Reeve Foundation, suggests that about 1 in 50 people have been diagnosed...
and vision problems with his right eye. Upon his discharge from the rehabilitation facility in July 1982, the full extent of KC’s neurological injuries was determined. He has severe injury to his medial temporal lobes, along with almost complete bilateral hippocampal loss. Ultimately, his neurological profile has stabilized, as seen in CT scans he has received once a decade since the accident.
Memory impairment
As a result of his neurological damage, K.C. suffered severe cognitive deficits that hindered his ability to form new episodic memories. However, both his semantic memorySemantic memory
Semantic memory refers to the memory of meanings, understandings, and other concept-based knowledge unrelated to specific experiences. The conscious recollection of factual information and general knowledge about the world is generally thought to be independent of context and personal relevance...
and noetic consciousness remained unimpaired. To illustrate this, research conducted on K.C. has shown that he is able to recall factual information that he learned prior to his accident, such as his ability to know the difference between stalactites and stalagmites. However, he is unable to remember emotional details of events from his past such as his brother’s death, the September 11 attacks, and a dangerous fall he had at his home.
K.C. also suffers from severe impairment of his Autonoetic consciousness
Autonoetic consciousness
Autonoetic consciousness is the human ability to mentally place ourselves in the past, in the future, or in counterfactual situations, and to analyze our own thoughts.Our sense of self affects our behavior, in the present, past and future...
. This means that he is unable to envision himself in the future. When asked what he would be doing later in a given day, month, or even a year, he was unable to respond with an answer. Just as he cannot remember being physically involved with events from his past, he is unable to imagine future events. Ultimately, he loses any memory of his current actions once his thoughts are directed elsewhere.
Neuropathologically, K.C suffers from both anterograde amnesia and temporally graded retrograde amnesia. Both forms of amnesia are characterized by damage to the medial temporal lobes, specifically within the hippocampal region. The trauma caused by K.C.’s accident has left him with severe anterograde amnesia that has made it impossible for him to remember both new personal experiences and semantic information. As far as his temporally graded retrograde amnesia is concerned, he is considered an anomaly; in other words, his ability to recall events prior to the accident is dependent on when those events occurred. Although he cannot remember personally experienced events, his semantic knowledge prior to his accident remained intact. His recollection of factual information in areas such as math, history and science, for example, were unaffected.
Legacy
Studies on K.C. have provided researchers with information on various topics in neuroscience.Memory storage & processing
Implications to K.C.’s neuropathology have shown that damage to specific regions of the brain is associated with different forms of memory loss. As a result of damage to K.C.’s medial temporal lobe, specifically his hippocampusHippocampus
The hippocampus is a major component of the brains of humans and other vertebrates. It belongs to the limbic system and plays important roles in the consolidation of information from short-term memory to long-term memory and spatial navigation. Humans and other mammals have two hippocampi, one in...
, research suggests that this area functions in processing episodic memory. However, damage to this area has left his semantic memory fully intact. This implies that episodic and semantic components of memory could be formed and stored separately, and thus processed by different regions of the brain.
Priming
PrimingPriming (psychology)
Priming is an implicit memory effect in which exposure to a stimulus influences a response to a later stimulus. It can occur following perceptual, semantic, or conceptual stimulus repetition...
studies on Patient K.C. revealed that individuals with severe amnesia can display intact priming capabilities regardless of episodic memory damage. Priming involves initially exposing a subject to a word or image so that a memory of that word or image can be formed. This is meant to improve a subject's recall of that word or image when that word or image is shown at a later time. Patient K.C. additionally showed that priming effects can last for long periods of time; in one study, researchers presented K.C. with a list of words, and after 12 months showed him the same words with letters missing. K.C. was able to complete these fragmented words as successfully as a person with normal brain function who was shown the same list initially. This challenged the previous opinion that patients with anterograde amnesia are incapable of adding information to their declarative memory
Declarative memory
Declarative memory is one of two types of long term human memory. It refers to memories which can be consciously recalled such as facts and knowledge. Its counterpart is known as non-declarative or Procedural memory, which refers to unconscious memories such as skills...
.
Semantic learning
Studies on Patient K.C. also illuminated the relationship between semantic learning and episodic memory, showing that patients with severe amnesia are capable of retaining new semantic knowledge in the absence of episodic memory. Researchers found that K.C. was able to learn new semantic knowledge and retain it over a long period of time. In one study, researchers taught K.C. 64 three-word sentences over multiple testing trials, and after 12 months, presented the same sentences to him with the last of the three words missing. K.C. showed significant retention of this semantic knowledge, completing 25 of the 64 sentences. This showed that amnesic patients can learn new semantic information, although slower than normal test subjects.Even though K.C. could not remember the actual teaching sessions, he was able to retain the raw information—the three-word sentences—presented to him. This showed that episodic and semantic memory are independent of one another, because K.C.’s episodic memory was not intact, but his declarative memory still functioned correctly. These findings show that acquisition of semantic knowledge is possible even if episodic memory is absent.
Research on Patient K.C. also led to greater understanding of priming in amnesics. Priming involves the exposure of a person to information under false pretenses. This information is ultimately recalled at a later period with the hope that the previous priming will improve recall ability. With respect to patient K.C., researchers found that successful priming is independent of both semantic and episodic memory. Episodic and semantic memory are therefore described as showing stochastic independence, ruling out the idea that K.C. was able to retain information because certain words were of greater significance to him than others.
Studies on K.C.’s semantic learning also provided insight into the conditions that are necessary to promote successful semantic learning in amnesic patients. Researchers found that maximizing amnesics’ ability to obtain new information requires efforts to minimize interference, which occurs when previously learned information prevents patients from correctly remembering subsequent information. The finding that interference significantly prevents successful semantic learning in amnesics provided explanation for why earlier experiments failed, as they did not make efforts to minimize interference.
Rehabilitation
Further studies on Patient K.C. tested the possibility of amnesia patients to learn information that was more complex than information acquired with priming. Researchers also examined if patients could learn information applicable to completing daily tasks. One study showed that K.C. could learn vocabulary associated with operating a desktop computer; further studies revealed that K.C. could actually learn commands related to computers to the extent that he was able to perform basic programming tasks on a microcomputer.Patient K.C.'s learning of this more complex information, however, was hyperspecific. When asked general questions about his tasks, K.C. could not explain the meaning behind the new information he had gained about computers. Similarly, if the command instructions he had learned were slightly changed, K.C. was unable to perform the programming tasks. This reflects that K.C. did not learn the meaning behind the information he had learned, and that he had formed only simple stimulus response connections. K.C.’s amnesia therefore involved both information loss and impairment of the processes that allow the integration of information to create an interconnected memory. Nevertheless, K.C. showed that severe anterograde amnesia does not restrict individuals from retaining knowledge that is more complex than information learned from priming.
See also
- Cognitive neuropsychologyCognitive neuropsychologyCognitive neuropsychology is a branch of cognitive psychology that aims to understand how the structure and function of the brain relates to specific psychological processes. It places a particular emphasis on studying the cognitive effects of brain injury or neurological illness with a view to...
- HM (patient)HM (patient)Henry Gustav Molaison , famously known as HM or H.M., was an American memory disorder patient who was widely studied from late 1957 until his death...
, an epileptic who had portions of his medial temporal lobe removed during surgery - Clive WearingClive WearingClive Wearing is a British musicologist, conductor, and keyboardist suffering from an acute and long-lasting case of anterograde and retrograde amnesia, meaning that he lacks the ability to form new memories.-Musical career:...
, whose amnesia was the result of herpes simplex encephalitis - Phineas GagePhineas GagePhineas P. Gage was an American railroad construction foreman now remembered for his improbablesurvival of an accident in which a large iron rod was driven completely through his head, destroying much of his brain's left frontal lobe, and for that injury's reported effects on his personality and...
, a 19th century railroad worker who had major personality changes after a traumatic brain injury