Article Figures & Data
Figures
- Figure 1.
Overview of the paradigm.
- Figure 2.
Behavioral results. Top, Accuracy of the entire group of 34 subjects, of the 11 patients, and of the 23 normal subjects as a function of memory load. Bottom, Reaction time. Error bars indicate SEM.
- Figure 3.
Positive shift of the DC potential during maintenance of a single item turning increasingly negative during maintenance of multiple items. Left column, Averaged hippocampal contacts; right column, averaged rhinal contacts in trials with one (light gray), two (dark gray), and four items (black).
- Figure 4.
Build-up of the negative shift of the DC potential during encoding of subsequent items in trials with four items. Left column, Averaged hippocampal contacts; right column, averaged rhinal contacts. Darker shades of gray indicate items later in the trial.
- Figure 5.
Decreased gamma power during maintenance of a single item and increasing gamma power during maintenance of multiple items. Trials with one item (left), two items (medium), and four items (right column). a, b, Power of iEEG from hippocampal (a) and rhinal (b) contacts. The plots on the right display normalized power values in the gamma frequency range (20–98 Hz) for trials with one item (light gray), two items (dark gray), and four items (black). Error bars indicate SEM.
- Figure 6.
Activation during encoding and maintenance period regardless of memory load. a, During encoding, we observed bilateral activation in the prefrontal cortex as well as in higher visual regions. Parameter estimates for different memory loads are shown for the contrast estimates in the most activated voxel in the left middle frontal gyrus (mean ± SD). b, Activation pattern during maintenance compared with rest. Parameter estimates are shown for the contrast estimates in the most activated voxel in the left inferior occipital gyrus (mean ± SD). In none of these contrasts did we observe an activation of MTL regions.
- Figure 7.
Memory load-dependent activation during processing of an increasing number of items during encoding and maintenance. a, b, Memory load-dependent hippocampal activation during encoding (a) and maintenance (b). The right column shows parameter estimates for contrast estimates of the most activated voxel in the left MTL in each condition (mean ± SD).
Tables
Region L/R BA MNI coordinates t score x y z Encoding > pause Middle frontal gyrus L 9 −42 9 30 7.96 Cuneus L 18 −12 −96 15 6.86 Middle frontal gyrus R 6 42 0 57 5.35 Medial superior frontal gyrus L 8 0 18 51 5.30 Middle frontal gyrus L 6 −45 3 57 4.27 Superior parietal gyrus R 7 24 −66 36 4.22 Lateral occipital gyrus R 19 36 −81 3 3.90 Insular cortex R 45 36 27 6 3.79 Maintenance > pause Inferior occipital gyrus L 18 −24 −93 −9 5.41 Posterior cingulate gyrus R 15 −39 12 5.23 Posterior cingulate gyrus L −18 −36 12 5.04 Fusiform gyrus L 19 −48 −66 −21 4.60 Middle temporal gyrus R 21 63 −30 −9 4.16 Medial superior frontal gyrus R 6 3 9 54 4.09 Middle temporal gyrus R 20 57 −39 −15 3.76 Memory load: encoding Lateral occipital gyrus L 18 −42 −84 −9 8.36 Lateral occipital gyrus R 19 39 −84 −6 6.94 Middle frontal gyrus L 9 −42 12 27 4.79 Superior colliculus L −6 −27 −12 4.75 Inferior frontal gyrus R 46 54 27 18 4.72 Superior occipital gyrus R 7 27 −72 33 4.48 Superior occipital gyrus L 19 −30 −72 33 4.46 Inferior frontal gyrus R 45 57 21 6 4.16 Hippocampus L −18 −30 −3 4.16 Medial superior frontal gyrus R 32 9 21 48 3.80 Inferior frontal gyrus R 9 48 15 30 3.76 Memory load: maintenance Hippocampus L 28 −24 −18 −12 4.29 Posterior corpus callosum R 12 −33 21 3.89 Alternative model separating early and late maintenance phase Memory load: early maintenance Middle temporal gyrus R 21 48 12 −33 4.57 Angular gyrus R 19 42 −81 36 4.45 Precuneus R 7 9 −63 45 4.36 Cerebellum R 15 −54 −21 3.98 Memory load: late maintenance Hippocampus L 28 −24 −21 −15 4.10 -
The table displays the coordinates of the maximally activated voxel in each activation cluster. L, Left; R, right; BA, Brodmann's area.
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Supplemental Data
Files in this Data Supplement:
- supplemental material - Figure legends
- supplemental material - Supplemental material
- supplemental material - Figure 1
- supplemental material - Figure 2
- supplemental material - Figure 3
- supplemental material - Figure 4
