Schmolck et al. (2002)

Outline

Aim(s)

To investigate the effects of damage to the medial temporal lobe (MTL) and anterolateral temporal cortex on semantic knowledge.

Procedure

They studied three post encephalitic amnesic patients with extensive MTL damage and variable damage to lateral temporal cortex, patient H.M. (whose damage is for the most part limited to the MTL but who has additional damage to anterolateral temporal cortex), two patients with lesions limited to the hippocampal formation (HF), and eight control subjects.

A series of nine tests involving 24 living and 24 non-living items was given, along with four additional tests of semantic knowledge.

Sample: 8 male controls; and 1 female and 5 male participants.

• Two participants had damage to the hippocampal formation (HF)

• Three participants had medial temporal lobe lesions with damage to the anterolateral temporal cortex (MTL+)

• HM had a bilateral medial temporal lobe resection for severe epilepsy.

All participants were given nine tests using the same line drawings from two categories; 24 in the category of ‘animals’ 24 from the category of ‘objects’.

Each of the 48 line drawings, or items, could also be assigned to one of 8 sub-categories. These were:

Non-living things

• 6 electrical household items

• 6 nonelectrical household items

• 6 vehicles

• 6 musical instruments

Living things

• 6 water creatures

• 6 birds

• 6 domestic land animals

• 6 foreign land animals

There was no time limit for the nine tests, unless specifically stated.

1. Pointing to Picture (cue: Name): Participants were given the name of an item as a cue and were asked to identify the appropriate picture from a selection of eight pictures that were from the same category (either animals or objects). They repeated this using all 48 items. Performance was measured as percentage correct answers.

2. Pointing to Picture (cue: Description): Participants were given a verbal description of an item as a cue (without mentioning the physical attributes) and asked to identify the appropriate picture from a selection of eight pictures that were from the same category (either animals or objects). They repeated this using all 48 items. Performance was measured as percentage correct answers.

3. Naming (cue: Picture): Participants were shown a picture of an item as a cue and then asked to name it. They repeated this using all 48 items. Performance was measured as percentage correct answers.

4. Naming (cue: Description): Participants were given a verbal description of an item as a cue and asked to name it. They repeated this using all 48 items. Performance was measured as percentage correct answers.

5. Semantic Features: Participants were asked a total of eight closed questions (requiring just ‘yes/no’ responses) about each item from a selection of 24 items. Four of the questions were about an item’s physical features, and four of the questions were about an item’s non-physical features. Examples of questions include; Is a toaster round? Does a zebra live in Africa? They repeated the process of asking the eight closed questions with all 24 items. Performance was measured as percentage correct answers.

6. Category Fluency: Participants were asked to name as many examples as they could from 8 sub-categories; four were of living things and four were of non-living things. This test was timed. For each of the eight categories, participants were given 1 min to respond with as many examples as they could, such as examples of vehicles. Performance was measured using a score for the total number of category examples that participants gave.

7. Category Sorting: Participants were asked to sort the pictures of all 48 items into one of two superordinate categories; living or manmade. They were then asked to sort the 24 items in each category into narrower ordinate categories, for example to sort the living items into land animals, birds, or water creatures or to sort the manmade things into household items, vehicles, or musical instruments. Finally, they sorted 12 land animals and 12 household items in three different ways using narrower subordinate categories; for example, they had to sort the land animals firstly into foreign or domestic animals, then again into fierce and non-fierce animals and again into animals larger or smaller than a German Shepherd dog. Performance was measured as percentage correct answers.

8. Definitions to Name: Participants were given the name of a least common item. They were then asked to define the item as if they were explaining it to someone who did not know what it was and has never seen it before. Schmolck et al had a card with the name of the item in view for the participants. This test was timed. Participants had 1 minute for each definition. This was repeated for the 24 least common items. The frequency of errors was measured in this test. Errors included incomplete or meaningless phrases and immediate repetitions of a phrase.

9. Definitions to Picture: Participants were shown a picture of a least common item and were asked to define this item. A line drawing of the item was in view for the participants. This test was timed. 1 min was allowed for each definition. This was repeated for the 24 least common items.

For tests 8 and 9, A tape-recorder was used and the definitions were then transcribed. Each participant’s performance was measured using the number of correct statements and the number of inaccurate statements. Schmolck et al also gave a quality score between 0 and 4 to each definition.

To assess the reliability of the 0–4 quality scoring method, they asked 14 raters to try to identify, from the transcripts for test 8, what items were being defined. Raters had to try to identify each item that was defined. They were then asked to quality score to each definition on the scale of 0–4.

A further four semantic tests were given to some of the participants and control group.

10. Pyramid and palm tree: Participants were given two test pictures and a target picture. They were asked which test picture went with the target picture. For example, a target picture of a saddle, with two test pictures of a horse and a goat. There were 52 cards used which each contained two test pictures and a target picture. Participants also repeated this study in a verbal condition, being given two test words and a target word.

11. Object/non-object discrimination: Participants were presented with a line drawing of an object and asked to identify if it was real or not. Non-real objects had been created by combining parts of real object. There were 30 objects and 30 non-objects presented in total.

12. Colouring object: Participants were asked to colour 28 line drawings of objects with the appropriate coloured pencil. Four different coloured pencils were provided to participants.

13. Nouns and verbs: Participants were asked to complete the second sentence of an example given to them. For example, ‘Everyday I take a banana. Just like everyday, yesterday I ______________ a banana’. In total, participants had to produce 64 irregular past tenses, 64 regular past tenses, 16 regular plurals and 16 irregular plurals.

Patients in the MTL group, as well as H.M. provided definitions with poor detail and a significant number of errors. They had difficulty making the items they were defining identifiable. This was the case when a picture of the item was in view, which controlled for impaired name comprehension.