n Pergamon P n o !Uv .No .I .pp+a?l rv94 .,11( , 1991 H'eo . S,- .-,,e in.1 Grea: nnwin . All ripha rernroRO et al . Who developed amnesia both had lesions in this area and the authors concluded that the reason for the severe memory deficit was the damage to both circuits of the limbic system . Furthermore it was stressed that the proximity of these two circuits 1n the anterior thalamus explained why a small lesion in this region of the brain could have such a disruptive effect on memory . It should he noted, however, that it may not he the amygdalar circuit that is critical to memory function . Rather it may be disruption of the projection from the perirhinal cortex, which lies adjacent to the amygdala, that is critically involved in causing memory impairment . This projection runs along the same route as the amygdala pathway and, given various lines of evidence that amygdalar lesions do not underlie amnesic impairment .. the critical involvement of the pcrirhinal cortical projection in memory impairments arising from damage in the anterior thalamic region seems quite probable (see SQCIR1L and ZoLA-MOR(iAN L24]) . The present study describes a patient who suffered a discrete thalamic infarction which damaged the thalamus in the anterior position identified by GRAFT-RADPORD el a1 .- thus providing an important test of these authors' conclusions concerning the minimal lesion required for diencephalic amnesia . Moreover, investigation of this patient enabled an investigation of the functional character of dieucephatic amnesia uncontaminated by the influence of additional frontal disturbance . CASE REPORT In November 1989 J .R ., a 48-year-old right-handed engineer, suffered a brief period of confusion and visual disturbance . Immediately following the incident fie experienced marked memory difficulties which included a mild nominal dysphasia . An MRI scan revealed a discrete left thalamic infarction which is illustrated in Fig . I . It can be seen that the lesion directly intersects the mamillothalamic tract and that there are also lesions in the dorsomedial nucleus and, to a lesser d egree . i n the ventro-lateral and centro-median nuclei . There was no evidence of any lesions elsewhere . The cause oft he infarction is not clear although it may be significant that J .R . had just recovered from a particularly severe Yer.ainia infection and had been indulging in vigorous exercise over a considerable period . ,Nruropsn'holopicat too is J .R . was administered the wecttslcr Memory Seal, [24] and It,, MQ was c csscd as Ion J R's per(onnwrce tugs uneven in that he shoved very good perlorniance on certain componeuns digit spaii i4) ,i,eiital control (9) . visual reproduetmn I1 2), orienlaIon lnforrnanon (5) hut poor performance on loge al memory (5) and paired associate learning (6 .5) . On the Weehsle, Adult Intelligence Scale I z8I 1 .R . s full scale IQ was 11) with some indication of poorer verhul than performance IQ (Verbal IQ= 10S, Perfornanec IQ= i20) . Performance on the Nationt,l Adult Reading Test (NART 115]) indicated a pirmorbid IQ o1' 114/1 I . Four tests of frontaI lobe tune non were administered . On the Wisconsin Card Sort ng Test (W CST, [to] I . J R . obtained all six categories but made 6 non-pcrscveralivc errors les'itlua normal range) . On IAS word fluency [2] THAI Axm UINFSiA 41 lie scored 37 [normal-CollInll group Imean age 51 .5, mean NART IQ I I8 5)=45 .'_ S .D .=9 .1] and he scored 0 on the Cognitive Estimation Test [20] which is also normal . On Trail Making LI] his A over B ratio was 1 .76 Inou lddilioiul psyrhological Cia!aolion 1 .R . was given anumber of additional tests in order to examine his menlore impairment n more detail . In all these tests a score of I S .D .greater or lesser than the comparison mean is considered evidence ofsignilicant Impairment . Poi cr! oesucintt' fearauntt :This was the same procedure as used by Lima and PARiIN [10] . The basic procedure involved Iearningalistoften paired associates to n criterion ofthreeconseculiveerrorless trials or for 10 trials . There weiC four conditions each invoh-ing different sets of word pairs . Rote learning (RL) . learning mcdialod by images presided by the experimenter I1 Pi . learning mediated by self-generated images IISOI, and learning mediated by experimenter supplied verbal information IYM i ,I .R's performance on this task was compared with the WKS patients reported in Ref [10] and a group of seven control subjects with 2 mean age of Sl'1 .S years, mean IQ INARTI 111 .3 . The data are shown in I' iii,2 and show thus I .R's performance is somewhat better than WKS patients in both RI-and VM conditions although, in comparison .vith controls he is markedly imptured . In contrast he is close to nominal on the image-modiutcd learning conditions Ills, [SG i . I eat unpin list in, .'rinrineti.rzt . J R was given a xcrsfon of the list discrimination procedure [23] . Both a verbal mind non-verbal version were administered . I'rrhcrl rersiwr Twenty-four Simple declarative sentences were dcvucd with I'_ designated targets and the remaining 12 disirnctors . The target sentences were fill the[ divided into two lists of six (designated List I and List ''-I . Subjects were told thel they would he shown two diferent sets of sentences, that they should try to remember finite, and to remember in which scl each nentcnec appeared- List I sentences wcrc presented one vet a tines , , Vol u I t a rate of one 5 sec and the snhicct was required to read each one aloud . After the last sentence there was a 3-min interval diI ing which the subject was engaged in light emversation with the experimenter . List 2 was then presented in the same manner u s List I . .After presentation of List'_ the subject was presented with a random sequenceof the 24 items comprising the targets from I .ists I and 2 plus the l.2 distractors . Items wcrc presented one a l u time and the suhjecl asked to decide whether or not each setitence had been shown before . [fit ''yes' response was given the subject was I'ucItci required la decide whether the sentence had peen in List I or List 11 ton rerba( rmsiow this was constructed in an identical fashion except than the 'A stimuli were all abstract designs .l .R's performance was cotnpard with a group of control subjects, mean age 51 .5 years . mean IQ INARTI I I5 .5, and . for the verbal condition only . the WKS patienls reported by fit yRIS :mod PARKIN 171, .1R was adminisierel the verbal tension twice with an interval of several weeks helwccn tests . Ttic results ul thccxperimenI areshown in Fig 3 . II isevidenl from this experiment UnitJ .R's reeugnillon memory liar the verbal stimuli is extremely poor in that his d"'core lies at the lower end of the WKS range_ In contrast his rcasgnitioii tnernorv for abstract designs is slightly above average . Iigure 3 also shows 1 .R 's lcntporal discrimination which s expressed t- t _score (see Appendix for an explanation of this measured . It can be seen that i .R .'s temporal discrimination is equally poor in both verbal and non-verbal conditions . Spin",! (is! ~Gso'intinution . This task is identical io the list discrimination task described above except that Lists I and 2 are dehnocl in terms ofspalial position (left or right (if subject( . New ntateriuls were devised and the resultant Lists I and 2 were arranged into I single random sequence with List I items being presented to the left and List 2 items to the right . At test subjects were I'crquired to stale whether they recognised each item rind . if yes, they also fettled whether it hid been presented to the left or tight .l .R, was compared with the some groups fuel in 01011s( discrimination experinicnt . I he results weree :tlculoted in I he same way as for temporal list discriminations rind ire summarised in I ig .4 .J .R's verbal recognition was again detective although somewhat better than in the lcntporal list discrimination task but his recogttttiott memory for abstract designs was normal. JR's improved performance an the verbal recognition component can he attributed to a methodological dilbrence between the tcmporul and spatial tests . In theformcr here is,i titres minute interval between the two lists whereas in the latter all 12 items arc presented as one sequence . As a result the first six items have to he remembered for a longer period in the tenspotd Ihau the spatial condition hence poorer performance-His spatial disci'iminatiun for verbal materials is lower than average but within normal limits FL, spatial discrimination for abstract designs "III well above the control setae . .S-vie, Te,t . In this task, devised by Hr SKIN [6] . the subjects were first presented with a sequence of 16 individually presented photographs . Half of the photographs were of the British countryside and the remainder depicted scones Goat a li,reign countryside . Suhjecls were told m look at each picture and decide whether each pictureShow e d a scene from either home or abroad . Ifollowing presentation of the bast picture subjects were then given r retention test . Each trial of the retention test involved presentation (if lout photographs and the subject had to pick out the target . Lach array comprised the target, a mirror image of the targe, plus two pictures of a novel scene on ofwhichwastheminnrimageoftheother .J .R .'sperformanceunthustaskwascomparedwith30subjects mean age 31 .5 years) and the III WKS patients reported in L7] Recognition was Judged correct if the subject chose either the target or its mirror image tend was measured as d' . Spatial discrimination was correct if the target was selected and measured using the a score procedure used in the I] A J . PniiU,C et rd . A 9 Icm A R I-ig . I IA,R) MRI diagram ., and scans showing position of 1R .', lesion in relation to principal Iflat anlie nuclei in the curonal planes A and R . Key. Ant--anterior nucleus ; (enl -cameo-median nuclam ; DM--dorso-medial nucleus : MTT-mamillothn[III nie t u1I . RN -red nuclerre SN subslanlia nigm : VL=ventn,Jaleral nucleus. VP central postero-lateen nucleus . other e,perimenls . I he results are shown in Fig 5 and show On 1 .R . . despite hcing much older than hit controls_ per tonned at a hiclicr keel oil the spatial discrimination component . I-:sldurti Ihai the lea is sen,ilir-c to amnesia impairment in is Indicated by the poor performance of the WAS patients_ Ren on m